/* * linux/fs/namei.c * * Copyright (C) 1991, 1992 Linus Torvalds */ /* * Some corrections by tytso. */ /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname * lookup logic. */ /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" #include "mount.h" /* [Feb-1997 T. Schoebel-Theuer] * Fundamental changes in the pathname lookup mechanisms (namei) * were necessary because of omirr. The reason is that omirr needs * to know the _real_ pathname, not the user-supplied one, in case * of symlinks (and also when transname replacements occur). * * The new code replaces the old recursive symlink resolution with * an iterative one (in case of non-nested symlink chains). It does * this with calls to _follow_link(). * As a side effect, dir_namei(), _namei() and follow_link() are now * replaced with a single function lookup_dentry() that can handle all * the special cases of the former code. * * With the new dcache, the pathname is stored at each inode, at least as * long as the refcount of the inode is positive. As a side effect, the * size of the dcache depends on the inode cache and thus is dynamic. * * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink * resolution to correspond with current state of the code. * * Note that the symlink resolution is not *completely* iterative. * There is still a significant amount of tail- and mid- recursion in * the algorithm. Also, note that _readlink() is not used in * lookup_dentry(): lookup_dentry() on the result of _readlink() * may return different results than _follow_link(). Many virtual * filesystems (including /proc) exhibit this behavior. */ /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL * and the name already exists in form of a symlink, try to create the new * name indicated by the symlink. The old code always complained that the * name already exists, due to not following the symlink even if its target * is nonexistent. The new semantics affects also mknod() and link() when * the name is a symlink pointing to a non-existent name. * * I don't know which semantics is the right one, since I have no access * to standards. But I found by trial that HP-UX 9.0 has the full "new" * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the * "old" one. Personally, I think the new semantics is much more logical. * Note that "ln old new" where "new" is a symlink pointing to a non-existing * file does succeed in both HP-UX and SunOs, but not in Solaris * and in the old Linux semantics. */ /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink * semantics. See the comments in "open_namei" and "do_link" below. * * [10-Sep-98 Alan Modra] Another symlink change. */ /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: * inside the path - always follow. * in the last component in creation/removal/renaming - never follow. * if LOOKUP_FOLLOW passed - follow. * if the pathname has trailing slashes - follow. * otherwise - don't follow. * (applied in that order). * * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT * restored for 2.4. This is the last surviving part of old 4.2BSD bug. * During the 2.4 we need to fix the userland stuff depending on it - * hopefully we will be able to get rid of that wart in 2.5. So far only * XEmacs seems to be relying on it... */ /* * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives * any extra contention... */ /* In order to reduce some races, while at the same time doing additional * checking and hopefully speeding things up, we copy filenames to the * kernel data space before using them.. * * POSIX.1 2.4: an empty pathname is invalid (ENOENT). * PATH_MAX includes the nul terminator --RR. */ static int do_getname(const char __user *filename, char *page) { int retval; unsigned long len = PATH_MAX; if (!segment_eq(get_fs(), KERNEL_DS)) { if ((unsigned long) filename >= TASK_SIZE) return -EFAULT; if (TASK_SIZE - (unsigned long) filename < PATH_MAX) len = TASK_SIZE - (unsigned long) filename; } retval = strncpy_from_user(page, filename, len); if (retval > 0) { if (retval < len) return 0; return -ENAMETOOLONG; } else if (!retval) retval = -ENOENT; return retval; } static char *getname_flags(const char __user *filename, int flags, int *empty) { char *tmp, *result; result = ERR_PTR(-ENOMEM); tmp = __getname(); if (tmp) { int retval = do_getname(filename, tmp); result = tmp; if (retval < 0) { if (retval == -ENOENT && empty) *empty = 1; if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) { __putname(tmp); result = ERR_PTR(retval); } } } audit_getname(result); return result; } char *getname(const char __user * filename) { return getname_flags(filename, 0, 0); } #ifdef CONFIG_AUDITSYSCALL void putname(const char *name) { if (unlikely(!audit_dummy_context())) audit_putname(name); else __putname(name); } EXPORT_SYMBOL(putname); #endif static int check_acl(struct inode *inode, int mask) { #ifdef CONFIG_FS_POSIX_ACL struct posix_acl *acl; if (mask & MAY_NOT_BLOCK) { acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); if (!acl) return -EAGAIN; /* no ->get_acl() calls in RCU mode... */ if (acl == ACL_NOT_CACHED) return -ECHILD; return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); } acl = get_cached_acl(inode, ACL_TYPE_ACCESS); /* * A filesystem can force a ACL callback by just never filling the * ACL cache. But normally you'd fill the cache either at inode * instantiation time, or on the first ->get_acl call. * * If the filesystem doesn't have a get_acl() function at all, we'll * just create the negative cache entry. */ if (acl == ACL_NOT_CACHED) { if (inode->i_op->get_acl) { acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS); if (IS_ERR(acl)) return PTR_ERR(acl); } else { set_cached_acl(inode, ACL_TYPE_ACCESS, NULL); return -EAGAIN; } } if (acl) { int error = posix_acl_permission(inode, acl, mask); posix_acl_release(acl); return error; } #endif return -EAGAIN; } /* * This does the basic permission checking */ static int acl_permission_check(struct inode *inode, int mask) { unsigned int mode = inode->i_mode; if (current_user_ns() != inode_userns(inode)) goto other_perms; if (likely(current_fsuid() == inode->i_uid)) mode >>= 6; else { if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { int error = check_acl(inode, mask); if (error != -EAGAIN) return error; } if (in_group_p(inode->i_gid)) mode >>= 3; } other_perms: /* * If the DACs are ok we don't need any capability check. */ if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) return 0; return -EACCES; } /** * generic_permission - check for access rights on a Posix-like filesystem * @inode: inode to check access rights for * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) * * Used to check for read/write/execute permissions on a file. * We use "fsuid" for this, letting us set arbitrary permissions * for filesystem access without changing the "normal" uids which * are used for other things. * * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk * request cannot be satisfied (eg. requires blocking or too much complexity). * It would then be called again in ref-walk mode. */ int generic_permission(struct inode *inode, int mask) { int ret; /* * Do the basic permission checks. */ ret = acl_permission_check(inode, mask); if (ret != -EACCES) return ret; if (S_ISDIR(inode->i_mode)) { /* DACs are overridable for directories */ if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE)) return 0; if (!(mask & MAY_WRITE)) if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH)) return 0; return -EACCES; } /* * Read/write DACs are always overridable. * Executable DACs are overridable when there is * at least one exec bit set. */ if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE)) return 0; /* * Searching includes executable on directories, else just read. */ mask &= MAY_READ | MAY_WRITE | MAY_EXEC; if (mask == MAY_READ) if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH)) return 0; return -EACCES; } /* * We _really_ want to just do "generic_permission()" without * even looking at the inode->i_op values. So we keep a cache * flag in inode->i_opflags, that says "this has not special * permission function, use the fast case". */ static inline int do_inode_permission(struct inode *inode, int mask) { if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { if (likely(inode->i_op->permission)) return inode->i_op->permission(inode, mask); /* This gets set once for the inode lifetime */ spin_lock(&inode->i_lock); inode->i_opflags |= IOP_FASTPERM; spin_unlock(&inode->i_lock); } return generic_permission(inode, mask); } /** * inode_permission - check for access rights to a given inode * @inode: inode to check permission on * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) * * Used to check for read/write/execute permissions on an inode. * We use "fsuid" for this, letting us set arbitrary permissions * for filesystem access without changing the "normal" uids which * are used for other things. * * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. */ int inode_permission(struct inode *inode, int mask) { int retval; if (unlikely(mask & MAY_WRITE)) { umode_t mode = inode->i_mode; /* * Nobody gets write access to a read-only fs. */ if (IS_RDONLY(inode) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) return -EROFS; /* * Nobody gets write access to an immutable file. */ if (IS_IMMUTABLE(inode)) return -EACCES; } retval = do_inode_permission(inode, mask); if (retval) return retval; retval = devcgroup_inode_permission(inode, mask); if (retval) return retval; return security_inode_permission(inode, mask); } /** * path_get - get a reference to a path * @path: path to get the reference to * * Given a path increment the reference count to the dentry and the vfsmount. */ void path_get(struct path *path) { mntget(path->mnt); dget(path->dentry); } EXPORT_SYMBOL(path_get); /** * path_put - put a reference to a path * @path: path to put the reference to * * Given a path decrement the reference count to the dentry and the vfsmount. */ void path_put(struct path *path) { dput(path->dentry); mntput(path->mnt); } EXPORT_SYMBOL(path_put); /* * Path walking has 2 modes, rcu-walk and ref-walk (see * Documentation/filesystems/path-lookup.txt). In situations when we can't * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab * normal reference counts on dentries and vfsmounts to transition to rcu-walk * mode. Refcounts are grabbed at the last known good point before rcu-walk * got stuck, so ref-walk may continue from there. If this is not successful * (eg. a seqcount has changed), then failure is returned and it's up to caller * to restart the path walk from the beginning in ref-walk mode. */ /** * unlazy_walk - try to switch to ref-walk mode. * @nd: nameidata pathwalk data * @dentry: child of nd->path.dentry or NULL * Returns: 0 on success, -ECHILD on failure * * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry * for ref-walk mode. @dentry must be a path found by a do_lookup call on * @nd or NULL. Must be called from rcu-walk context. */ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) { struct fs_struct *fs = current->fs; struct dentry *parent = nd->path.dentry; int want_root = 0; BUG_ON(!(nd->flags & LOOKUP_RCU)); if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { want_root = 1; spin_lock(&fs->lock); if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry) goto err_root; } spin_lock(&parent->d_lock); if (!dentry) { if (!__d_rcu_to_refcount(parent, nd->seq)) goto err_parent; BUG_ON(nd->inode != parent->d_inode); } else { if (dentry->d_parent != parent) goto err_parent; spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); if (!__d_rcu_to_refcount(dentry, nd->seq)) goto err_child; /* * If the sequence check on the child dentry passed, then * the child has not been removed from its parent. This * means the parent dentry must be valid and able to take * a reference at this point. */ BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent); BUG_ON(!parent->d_count); parent->d_count++; spin_unlock(&dentry->d_lock); } spin_unlock(&parent->d_lock); if (want_root) { path_get(&nd->root); spin_unlock(&fs->lock); } mntget(nd->path.mnt); rcu_read_unlock(); br_read_unlock(vfsmount_lock); nd->flags &= ~LOOKUP_RCU; return 0; err_child: spin_unlock(&dentry->d_lock); err_parent: spin_unlock(&parent->d_lock); err_root: if (want_root) spin_unlock(&fs->lock); return -ECHILD; } /** * release_open_intent - free up open intent resources * @nd: pointer to nameidata */ void release_open_intent(struct nameidata *nd) { struct file *file = nd->intent.open.file; if (file && !IS_ERR(file)) { if (file->f_path.dentry == NULL) put_filp(file); else fput(file); } } static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd) { return dentry->d_op->d_revalidate(dentry, nd); } /** * complete_walk - successful completion of path walk * @nd: pointer nameidata * * If we had been in RCU mode, drop out of it and legitimize nd->path. * Revalidate the final result, unless we'd already done that during * the path walk or the filesystem doesn't ask for it. Return 0 on * success, -error on failure. In case of failure caller does not * need to drop nd->path. */ static int complete_walk(struct nameidata *nd) { struct dentry *dentry = nd->path.dentry; int status; if (nd->flags & LOOKUP_RCU) { nd->flags &= ~LOOKUP_RCU; if (!(nd->flags & LOOKUP_ROOT)) nd->root.mnt = NULL; spin_lock(&dentry->d_lock); if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) { spin_unlock(&dentry->d_lock); rcu_read_unlock(); br_read_unlock(vfsmount_lock); return -ECHILD; } BUG_ON(nd->inode != dentry->d_inode); spin_unlock(&dentry->d_lock); mntget(nd->path.mnt); rcu_read_unlock(); br_read_unlock(vfsmount_lock); } if (likely(!(nd->flags & LOOKUP_JUMPED))) return 0; if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE))) return 0; if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT))) return 0; /* Note: we do not d_invalidate() */ status = d_revalidate(dentry, nd); if (status > 0) return 0; if (!status) status = -ESTALE; path_put(&nd->path); return status; } static __always_inline void set_root(struct nameidata *nd) { if (!nd->root.mnt) get_fs_root(current->fs, &nd->root); } static int link_path_walk(const char *, struct nameidata *); static __always_inline void set_root_rcu(struct nameidata *nd) { if (!nd->root.mnt) { struct fs_struct *fs = current->fs; unsigned seq; do { seq = read_seqcount_begin(&fs->seq); nd->root = fs->root; nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq); } while (read_seqcount_retry(&fs->seq, seq)); } } static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link) { int ret; if (IS_ERR(link)) goto fail; if (*link == '/') { set_root(nd); path_put(&nd->path); nd->path = nd->root; path_get(&nd->root); nd->flags |= LOOKUP_JUMPED; } nd->inode = nd->path.dentry->d_inode; ret = link_path_walk(link, nd); return ret; fail: path_put(&nd->path); return PTR_ERR(link); } static void path_put_conditional(struct path *path, struct nameidata *nd) { dput(path->dentry); if (path->mnt != nd->path.mnt) mntput(path->mnt); } static inline void path_to_nameidata(const struct path *path, struct nameidata *nd) { if (!(nd->flags & LOOKUP_RCU)) { dput(nd->path.dentry); if (nd->path.mnt != path->mnt) mntput(nd->path.mnt); } nd->path.mnt = path->mnt; nd->path.dentry = path->dentry; } static inline void put_link(struct nameidata *nd, struct path *link, void *cookie) { struct inode *inode = link->dentry->d_inode; if (!IS_ERR(cookie) && inode->i_op->put_link) inode->i_op->put_link(link->dentry, nd, cookie); path_put(link); } static __always_inline int follow_link(struct path *link, struct nameidata *nd, void **p) { int error; struct dentry *dentry = link->dentry; BUG_ON(nd->flags & LOOKUP_RCU); if (link->mnt == nd->path.mnt) mntget(link->mnt); if (unlikely(current->total_link_count >= 40)) { *p = ERR_PTR(-ELOOP); /* no ->put_link(), please */ path_put(&nd->path); return -ELOOP; } cond_resched(); current->total_link_count++; touch_atime(link->mnt, dentry); nd_set_link(nd, NULL); error = security_inode_follow_link(link->dentry, nd); if (error) { *p = ERR_PTR(error); /* no ->put_link(), please */ path_put(&nd->path); return error; } nd->last_type = LAST_BIND; *p = dentry->d_inode->i_op->follow_link(dentry, nd); error = PTR_ERR(*p); if (!IS_ERR(*p)) { char *s = nd_get_link(nd); error = 0; if (s) error = __vfs_follow_link(nd, s); else if (nd->last_type == LAST_BIND) { nd->flags |= LOOKUP_JUMPED; nd->inode = nd->path.dentry->d_inode; if (nd->inode->i_op->follow_link) { /* stepped on a _really_ weird one */ path_put(&nd->path); error = -ELOOP; } } } return error; } static int follow_up_rcu(struct path *path) { struct mount *mnt = real_mount(path->mnt); struct mount *parent; struct dentry *mountpoint; parent = mnt->mnt_parent; if (&parent->mnt == path->mnt) return 0; mountpoint = mnt->mnt.mnt_mountpoint; path->dentry = mountpoint; path->mnt = &parent->mnt; return 1; } int follow_up(struct path *path) { struct mount *mnt = real_mount(path->mnt); struct mount *parent; struct dentry *mountpoint; br_read_lock(vfsmount_lock); parent = mnt->mnt_parent; if (&parent->mnt == path->mnt) { br_read_unlock(vfsmount_lock); return 0; } mntget(&parent->mnt); mountpoint = dget(mnt->mnt.mnt_mountpoint); br_read_unlock(vfsmount_lock); dput(path->dentry); path->dentry = mountpoint; mntput(path->mnt); path->mnt = &parent->mnt; return 1; } /* * Perform an automount * - return -EISDIR to tell follow_managed() to stop and return the path we * were called with. */ static int follow_automount(struct path *path, unsigned flags, bool *need_mntput) { struct vfsmount *mnt; int err; if (!path->dentry->d_op || !path->dentry->d_op->d_automount) return -EREMOTE; /* We don't want to mount if someone's just doing a stat - * unless they're stat'ing a directory and appended a '/' to * the name. * * We do, however, want to mount if someone wants to open or * create a file of any type under the mountpoint, wants to * traverse through the mountpoint or wants to open the * mounted directory. Also, autofs may mark negative dentries * as being automount points. These will need the attentions * of the daemon to instantiate them before they can be used. */ if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && path->dentry->d_inode) return -EISDIR; current->total_link_count++; if (current->total_link_count >= 40) return -ELOOP; mnt = path->dentry->d_op->d_automount(path); if (IS_ERR(mnt)) { /* * The filesystem is allowed to return -EISDIR here to indicate * it doesn't want to automount. For instance, autofs would do * this so that its userspace daemon can mount on this dentry. * * However, we can only permit this if it's a terminal point in * the path being looked up; if it wasn't then the remainder of * the path is inaccessible and we should say so. */ if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT)) return -EREMOTE; return PTR_ERR(mnt); } if (!mnt) /* mount collision */ return 0; if (!*need_mntput) { /* lock_mount() may release path->mnt on error */ mntget(path->mnt); *need_mntput = true; } err = finish_automount(mnt, path); switch (err) { case -EBUSY: /* Someone else made a mount here whilst we were busy */ return 0; case 0: path_put(path); path->mnt = mnt; path->dentry = dget(mnt->mnt_root); return 0; default: return err; } } /* * Handle a dentry that is managed in some way. * - Flagged for transit management (autofs) * - Flagged as mountpoint * - Flagged as automount point * * This may only be called in refwalk mode. * * Serialization is taken care of in namespace.c */ static int follow_managed(struct path *path, unsigned flags) { struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ unsigned managed; bool need_mntput = false; int ret = 0; /* Given that we're not holding a lock here, we retain the value in a * local variable for each dentry as we look at it so that we don't see * the components of that value change under us */ while (managed = ACCESS_ONCE(path->dentry->d_flags), managed &= DCACHE_MANAGED_DENTRY, unlikely(managed != 0)) { /* Allow the filesystem to manage the transit without i_mutex * being held. */ if (managed & DCACHE_MANAGE_TRANSIT) { BUG_ON(!path->dentry->d_op); BUG_ON(!path->dentry->d_op->d_manage); ret = path->dentry->d_op->d_manage(path->dentry, false); if (ret < 0) break; } /* Transit to a mounted filesystem. */ if (managed & DCACHE_MOUNTED) { struct vfsmount *mounted = lookup_mnt(path); if (mounted) { dput(path->dentry); if (need_mntput) mntput(path->mnt); path->mnt = mounted; path->dentry = dget(mounted->mnt_root); need_mntput = true; continue; } /* Something is mounted on this dentry in another * namespace and/or whatever was mounted there in this * namespace got unmounted before we managed to get the * vfsmount_lock */ } /* Handle an automount point */ if (managed & DCACHE_NEED_AUTOMOUNT) { ret = follow_automount(path, flags, &need_mntput); if (ret < 0) break; continue; } /* We didn't change the current path point */ break; } if (need_mntput && path->mnt == mnt) mntput(path->mnt); if (ret == -EISDIR) ret = 0; return ret < 0 ? ret : need_mntput; } int follow_down_one(struct path *path) { struct vfsmount *mounted; mounted = lookup_mnt(path); if (mounted) { dput(path->dentry); mntput(path->mnt); path->mnt = mounted; path->dentry = dget(mounted->mnt_root); return 1; } return 0; } static inline bool managed_dentry_might_block(struct dentry *dentry) { return (dentry->d_flags & DCACHE_MANAGE_TRANSIT && dentry->d_op->d_manage(dentry, true) < 0); } /* * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if * we meet a managed dentry that would need blocking. */ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, struct inode **inode) { for (;;) { struct mount *mounted; /* * Don't forget we might have a non-mountpoint managed dentry * that wants to block transit. */ if (unlikely(managed_dentry_might_block(path->dentry))) return false; if (!d_mountpoint(path->dentry)) break; mounted = __lookup_mnt(path->mnt, path->dentry, 1); if (!mounted) break; path->mnt = &mounted->mnt; path->dentry = mounted->mnt.mnt_root; nd->flags |= LOOKUP_JUMPED; nd->seq = read_seqcount_begin(&path->dentry->d_seq); /* * Update the inode too. We don't need to re-check the * dentry sequence number here after this d_inode read, * because a mount-point is always pinned. */ *inode = path->dentry->d_inode; } return true; } static void follow_mount_rcu(struct nameidata *nd) { while (d_mountpoint(nd->path.dentry)) { struct mount *mounted; mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1); if (!mounted) break; nd->path.mnt = &mounted->mnt; nd->path.dentry = mounted->mnt.mnt_root; nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); } } static int follow_dotdot_rcu(struct nameidata *nd) { set_root_rcu(nd); while (1) { if (nd->path.dentry == nd->root.dentry && nd->path.mnt == nd->root.mnt) { break; } if (nd->path.dentry != nd->path.mnt->mnt_root) { struct dentry *old = nd->path.dentry; struct dentry *parent = old->d_parent; unsigned seq; seq = read_seqcount_begin(&parent->d_seq); if (read_seqcount_retry(&old->d_seq, nd->seq)) goto failed; nd->path.dentry = parent; nd->seq = seq; break; } if (!follow_up_rcu(&nd->path)) break; nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); } follow_mount_rcu(nd); nd->inode = nd->path.dentry->d_inode; return 0; failed: nd->flags &= ~LOOKUP_RCU; if (!(nd->flags & LOOKUP_ROOT)) nd->root.mnt = NULL; rcu_read_unlock(); br_read_unlock(vfsmount_lock); return -ECHILD; } /* * Follow down to the covering mount currently visible to userspace. At each * point, the filesystem owning that dentry may be queried as to whether the * caller is permitted to proceed or not. */ int follow_down(struct path *path) { unsigned managed; int ret; while (managed = ACCESS_ONCE(path->dentry->d_flags), unlikely(managed & DCACHE_MANAGED_DENTRY)) { /* Allow the filesystem to manage the transit without i_mutex * being held. * * We indicate to the filesystem if someone is trying to mount * something here. This gives autofs the chance to deny anyone * other than its daemon the right to mount on its * superstructure. * * The filesystem may sleep at this point. */ if (managed & DCACHE_MANAGE_TRANSIT) { BUG_ON(!path->dentry->d_op); BUG_ON(!path->dentry->d_op->d_manage); ret = path->dentry->d_op->d_manage( path->dentry, false); if (ret < 0) return ret == -EISDIR ? 0 : ret; } /* Transit to a mounted filesystem. */ if (managed & DCACHE_MOUNTED) { struct vfsmount *mounted = lookup_mnt(path); if (!mounted) break; dput(path->dentry); mntput(path->mnt); path->mnt = mounted; path->dentry = dget(mounted->mnt_root); continue; } /* Don't handle automount points here */ break; } return 0; } /* * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() */ static void follow_mount(struct path *path) { while (d_mountpoint(path->dentry)) { struct vfsmount *mounted = lookup_mnt(path); if (!mounted) break; dput(path->dentry); mntput(path->mnt); path->mnt = mounted; path->dentry = dget(mounted->mnt_root); } } static void follow_dotdot(struct nameidata *nd) { set_root(nd); while(1) { struct dentry *old = nd->path.dentry; if (nd->path.dentry == nd->root.dentry && nd->path.mnt == nd->root.mnt) { break; } if (nd->path.dentry != nd->path.mnt->mnt_root) { /* rare case of legitimate dget_parent()... */ nd->path.dentry = dget_parent(nd->path.dentry); dput(old); break; } if (!follow_up(&nd->path)) break; } follow_mount(&nd->path); nd->inode = nd->path.dentry->d_inode; } /* * Allocate a dentry with name and parent, and perform a parent * directory ->lookup on it. Returns the new dentry, or ERR_PTR * on error. parent->d_inode->i_mutex must be held. d_lookup must * have verified that no child exists while under i_mutex. */ static struct dentry *d_alloc_and_lookup(struct dentry *parent, struct qstr *name, struct nameidata *nd) { struct inode *inode = parent->d_inode; struct dentry *dentry; struct dentry *old; /* Don't create child dentry for a dead directory. */ if (unlikely(IS_DEADDIR(inode))) return ERR_PTR(-ENOENT); dentry = d_alloc(parent, name); if (unlikely(!dentry)) return ERR_PTR(-ENOMEM); old = inode->i_op->lookup(inode, dentry, nd); if (unlikely(old)) { dput(dentry); dentry = old; } return dentry; } /* * We already have a dentry, but require a lookup to be performed on the parent * directory to fill in d_inode. Returns the new dentry, or ERR_PTR on error. * parent->d_inode->i_mutex must be held. d_lookup must have verified that no * child exists while under i_mutex. */ static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentry, struct nameidata *nd) { struct inode *inode = parent->d_inode; struct dentry *old; /* Don't create child dentry for a dead directory. */ if (unlikely(IS_DEADDIR(inode))) return ERR_PTR(-ENOENT); old = inode->i_op->lookup(inode, dentry, nd); if (unlikely(old)) { dput(dentry); dentry = old; } return dentry; } /* * It's more convoluted than I'd like it to be, but... it's still fairly * small and for now I'd prefer to have fast path as straight as possible. * It _is_ time-critical. */ static int do_lookup(struct nameidata *nd, struct qstr *name, struct path *path, struct inode **inode) { struct vfsmount *mnt = nd->path.mnt; struct dentry *dentry, *parent = nd->path.dentry; int need_reval = 1; int status = 1; int err; /* * Rename seqlock is not required here because in the off chance * of a false negative due to a concurrent rename, we're going to * do the non-racy lookup, below. */ if (nd->flags & LOOKUP_RCU) { unsigned seq; *inode = nd->inode; dentry = __d_lookup_rcu(parent, name, &seq, inode); if (!dentry) goto unlazy; /* Memory barrier in read_seqcount_begin of child is enough */ if (__read_seqcount_retry(&parent->d_seq, nd->seq)) return -ECHILD; nd->seq = seq; if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { status = d_revalidate(dentry, nd); if (unlikely(status <= 0)) { if (status != -ECHILD) need_reval = 0; goto unlazy; } } if (unlikely(d_need_lookup(dentry))) goto unlazy; path->mnt = mnt; path->dentry = dentry; if (unlikely(!__follow_mount_rcu(nd, path, inode))) goto unlazy; if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT)) goto unlazy; return 0; unlazy: if (unlazy_walk(nd, dentry)) return -ECHILD; } else { dentry = __d_lookup(parent, name); } if (dentry && unlikely(d_need_lookup(dentry))) { dput(dentry); dentry = NULL; } retry: if (unlikely(!dentry)) { struct inode *dir = parent->d_inode; BUG_ON(nd->inode != dir); mutex_lock(&dir->i_mutex); dentry = d_lookup(parent, name); if (likely(!dentry)) { dentry = d_alloc_and_lookup(parent, name, nd); if (IS_ERR(dentry)) { mutex_unlock(&dir->i_mutex); return PTR_ERR(dentry); } /* known good */ need_reval = 0; status = 1; } else if (unlikely(d_need_lookup(dentry))) { dentry = d_inode_lookup(parent, dentry, nd); if (IS_ERR(dentry)) { mutex_unlock(&dir->i_mutex); return PTR_ERR(dentry); } /* known good */ need_reval = 0; status = 1; } mutex_unlock(&dir->i_mutex); } if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) status = d_revalidate(dentry, nd); if (unlikely(status <= 0)) { if (status < 0) { dput(dentry); return status; } if (!d_invalidate(dentry)) { dput(dentry); dentry = NULL; need_reval = 1; goto retry; } } path->mnt = mnt; path->dentry = dentry; err = follow_managed(path, nd->flags); if (unlikely(err < 0)) { path_put_conditional(path, nd); return err; } if (err) nd->flags |= LOOKUP_JUMPED; *inode = path->dentry->d_inode; return 0; } static inline int may_lookup(struct nameidata *nd) { if (nd->flags & LOOKUP_RCU) { int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); if (err != -ECHILD) return err; if (unlazy_walk(nd, NULL)) return -ECHILD; } return inode_permission(nd->inode, MAY_EXEC); } static inline int handle_dots(struct nameidata *nd, int type) { if (type == LAST_DOTDOT) { if (nd->flags & LOOKUP_RCU) { if (follow_dotdot_rcu(nd)) return -ECHILD; } else follow_dotdot(nd); } return 0; } static void terminate_walk(struct nameidata *nd) { if (!(nd->flags & LOOKUP_RCU)) { path_put(&nd->path); } else { nd->flags &= ~LOOKUP_RCU; if (!(nd->flags & LOOKUP_ROOT)) nd->root.mnt = NULL; rcu_read_unlock(); br_read_unlock(vfsmount_lock); } } /* * Do we need to follow links? We _really_ want to be able * to do this check without having to look at inode->i_op, * so we keep a cache of "no, this doesn't need follow_link" * for the common case. */ static inline int should_follow_link(struct inode *inode, int follow) { if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) { if (likely(inode->i_op->follow_link)) return follow; /* This gets set once for the inode lifetime */ spin_lock(&inode->i_lock); inode->i_opflags |= IOP_NOFOLLOW; spin_unlock(&inode->i_lock); } return 0; } static inline int walk_component(struct nameidata *nd, struct path *path, struct qstr *name, int type, int follow) { struct inode *inode; int err; /* * "." and ".." are special - ".." especially so because it has * to be able to know about the current root directory and * parent relationships. */ if (unlikely(type != LAST_NORM)) return handle_dots(nd, type); err = do_lookup(nd, name, path, &inode); if (unlikely(err)) { terminate_walk(nd); return err; } if (!inode) { path_to_nameidata(path, nd); terminate_walk(nd); return -ENOENT; } if (should_follow_link(inode, follow)) { if (nd->flags & LOOKUP_RCU) { if (unlikely(unlazy_walk(nd, path->dentry))) { terminate_walk(nd); return -ECHILD; } } BUG_ON(inode != path->dentry->d_inode); return 1; } path_to_nameidata(path, nd); nd->inode = inode; return 0; } /* * This limits recursive symlink follows to 8, while * limiting consecutive symlinks to 40. * * Without that kind of total limit, nasty chains of consecutive * symlinks can cause almost arbitrarily long lookups. */ static inline int nested_symlink(struct path *path, struct nameidata *nd) { int res; if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { path_put_conditional(path, nd); path_put(&nd->path); return -ELOOP; } BUG_ON(nd->depth >= MAX_NESTED_LINKS); nd->depth++; current->link_count++; do { struct path link = *path; void *cookie; res = follow_link(&link, nd, &cookie); if (!res) res = walk_component(nd, path, &nd->last, nd->last_type, LOOKUP_FOLLOW); put_link(nd, &link, cookie); } while (res > 0); current->link_count--; nd->depth--; return res; } /* * We really don't want to look at inode->i_op->lookup * when we don't have to. So we keep a cache bit in * the inode ->i_opflags field that says "yes, we can * do lookup on this inode". */ static inline int can_lookup(struct inode *inode) { if (likely(inode->i_opflags & IOP_LOOKUP)) return 1; if (likely(!inode->i_op->lookup)) return 0; /* We do this once for the lifetime of the inode */ spin_lock(&inode->i_lock); inode->i_opflags |= IOP_LOOKUP; spin_unlock(&inode->i_lock); return 1; } /* * Name resolution. * This is the basic name resolution function, turning a pathname into * the final dentry. We expect 'base' to be positive and a directory. * * Returns 0 and nd will have valid dentry and mnt on success. * Returns error and drops reference to input namei data on failure. */ static int link_path_walk(const char *name, struct nameidata *nd) { struct path next; int err; while (*name=='/') name++; if (!*name) return 0; /* At this point we know we have a real path component. */ for(;;) { unsigned long hash; struct qstr this; unsigned int c; int type; err = may_lookup(nd); if (err) break; this.name = name; c = *(const unsigned char *)name; hash = init_name_hash(); do { name++; hash = partial_name_hash(c, hash); c = *(const unsigned char *)name; } while (c && (c != '/')); this.len = name - (const char *) this.name; this.hash = end_name_hash(hash); type = LAST_NORM; if (this.name[0] == '.') switch (this.len) { case 2: if (this.name[1] == '.') { type = LAST_DOTDOT; nd->flags |= LOOKUP_JUMPED; } break; case 1: type = LAST_DOT; } if (likely(type == LAST_NORM)) { struct dentry *parent = nd->path.dentry; nd->flags &= ~LOOKUP_JUMPED; if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { err = parent->d_op->d_hash(parent, nd->inode, &this); if (err < 0) break; } } /* remove trailing slashes? */ if (!c) goto last_component; while (*++name == '/'); if (!*name) goto last_component; err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW); if (err < 0) return err; if (err) { err = nested_symlink(&next, nd); if (err) return err; } if (can_lookup(nd->inode)) continue; err = -ENOTDIR; break; /* here ends the main loop */ last_component: nd->last = this; nd->last_type = type; return 0; } terminate_walk(nd); return err; } static int path_init(int dfd, const char *name, unsigned int flags, struct nameidata *nd, struct file **fp) { int retval = 0; int fput_needed; struct file *file; nd->last_type = LAST_ROOT; /* if there are only slashes... */ nd->flags = flags | LOOKUP_JUMPED; nd->depth = 0; if (flags & LOOKUP_ROOT) { struct inode *inode = nd->root.dentry->d_inode; if (*name) { if (!inode->i_op->lookup) return -ENOTDIR; retval = inode_permission(inode, MAY_EXEC); if (retval) return retval; } nd->path = nd->root; nd->inode = inode; if (flags & LOOKUP_RCU) { br_read_lock(vfsmount_lock); rcu_read_lock(); nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); } else { path_get(&nd->path); } return 0; } nd->root.mnt = NULL; if (*name=='/') { if (flags & LOOKUP_RCU) { br_read_lock(vfsmount_lock); rcu_read_lock(); set_root_rcu(nd); } else { set_root(nd); path_get(&nd->root); } nd->path = nd->root; } else if (dfd == AT_FDCWD) { if (flags & LOOKUP_RCU) { struct fs_struct *fs = current->fs; unsigned seq; br_read_lock(vfsmount_lock); rcu_read_lock(); do { seq = read_seqcount_begin(&fs->seq); nd->path = fs->pwd; nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); } while (read_seqcount_retry(&fs->seq, seq)); } else { get_fs_pwd(current->fs, &nd->path); } } else { struct dentry *dentry; file = fget_raw_light(dfd, &fput_needed); retval = -EBADF; if (!file) goto out_fail; dentry = file->f_path.dentry; if (*name) { retval = -ENOTDIR; if (!S_ISDIR(dentry->d_inode->i_mode)) goto fput_fail; retval = inode_permission(dentry->d_inode, MAY_EXEC); if (retval) goto fput_fail; } nd->path = file->f_path; if (flags & LOOKUP_RCU) { if (fput_needed) *fp = file; nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); br_read_lock(vfsmount_lock); rcu_read_lock(); } else { path_get(&file->f_path); fput_light(file, fput_needed); } } nd->inode = nd->path.dentry->d_inode; return 0; fput_fail: fput_light(file, fput_needed); out_fail: return retval; } static inline int lookup_last(struct nameidata *nd, struct path *path) { if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; nd->flags &= ~LOOKUP_PARENT; return walk_component(nd, path, &nd->last, nd->last_type, nd->flags & LOOKUP_FOLLOW); } /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ static int path_lookupat(int dfd, const char *name, unsigned int flags, struct nameidata *nd) { struct file *base = NULL; struct path path; int err; /* * Path walking is largely split up into 2 different synchronisation * schemes, rcu-walk and ref-walk (explained in * Documentation/filesystems/path-lookup.txt). These share much of the * path walk code, but some things particularly setup, cleanup, and * following mounts are sufficiently divergent that functions are * duplicated. Typically there is a function foo(), and its RCU * analogue, foo_rcu(). * * -ECHILD is the error number of choice (just to avoid clashes) that * is returned if some aspect of an rcu-walk fails. Such an error must * be handled by restarting a traditional ref-walk (which will always * be able to complete). */ err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base); if (unlikely(err)) return err; current->total_link_count = 0; err = link_path_walk(name, nd); if (!err && !(flags & LOOKUP_PARENT)) { err = lookup_last(nd, &path); while (err > 0) { void *cookie; struct path link = path; nd->flags |= LOOKUP_PARENT; err = follow_link(&link, nd, &cookie); if (!err) err = lookup_last(nd, &path); put_link(nd, &link, cookie); } } if (!err) err = complete_walk(nd); if (!err && nd->flags & LOOKUP_DIRECTORY) { if (!nd->inode->i_op->lookup) { path_put(&nd->path); err = -ENOTDIR; } } if (base) fput(base); if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { path_put(&nd->root); nd->root.mnt = NULL; } return err; } static int do_path_lookup(int dfd, const char *name, unsigned int flags, struct nameidata *nd) { int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd); if (unlikely(retval == -ECHILD)) retval = path_lookupat(dfd, name, flags, nd); if (unlikely(retval == -ESTALE)) retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd); if (likely(!retval)) { if (unlikely(!audit_dummy_context())) { if (nd->path.dentry && nd->inode) audit_inode(name, nd->path.dentry); } } return retval; } int kern_path_parent(const char *name, struct nameidata *nd) { return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd); } int kern_path(const char *name, unsigned int flags, struct path *path) { struct nameidata nd; int res = do_path_lookup(AT_FDCWD, name, flags, &nd); if (!res) *path = nd.path; return res; } /** * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair * @dentry: pointer to dentry of the base directory * @mnt: pointer to vfs mount of the base directory * @name: pointer to file name * @flags: lookup flags * @path: pointer to struct path to fill */ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, const char *name, unsigned int flags, struct path *path) { struct nameidata nd; int err; nd.root.dentry = dentry; nd.root.mnt = mnt; BUG_ON(flags & LOOKUP_PARENT); /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */ err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd); if (!err) *path = nd.path; return err; } static struct dentry *__lookup_hash(struct qstr *name, struct dentry *base, struct nameidata *nd) { struct inode *inode = base->d_inode; struct dentry *dentry; int err; err = inode_permission(inode, MAY_EXEC); if (err) return ERR_PTR(err); /* * Don't bother with __d_lookup: callers are for creat as * well as unlink, so a lot of the time it would cost * a double lookup. */ dentry = d_lookup(base, name); if (dentry && d_need_lookup(dentry)) { /* * __lookup_hash is called with the parent dir's i_mutex already * held, so we are good to go here. */ dentry = d_inode_lookup(base, dentry, nd); if (IS_ERR(dentry)) return dentry; } if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE)) { int status = d_revalidate(dentry, nd); if (unlikely(status <= 0)) { /* * The dentry failed validation. * If d_revalidate returned 0 attempt to invalidate * the dentry otherwise d_revalidate is asking us * to return a fail status. */ if (status < 0) { dput(dentry); return ERR_PTR(status); } else if (!d_invalidate(dentry)) { dput(dentry); dentry = NULL; } } } if (!dentry) dentry = d_alloc_and_lookup(base, name, nd); return dentry; } /* * Restricted form of lookup. Doesn't follow links, single-component only, * needs parent already locked. Doesn't follow mounts. * SMP-safe. */ static struct dentry *lookup_hash(struct nameidata *nd) { return __lookup_hash(&nd->last, nd->path.dentry, nd); } /** * lookup_one_len - filesystem helper to lookup single pathname component * @name: pathname component to lookup * @base: base directory to lookup from * @len: maximum length @len should be interpreted to * * Note that this routine is purely a helper for filesystem usage and should * not be called by generic code. Also note that by using this function the * nameidata argument is passed to the filesystem methods and a filesystem * using this helper needs to be prepared for that. */ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) { struct qstr this; unsigned long hash; unsigned int c; WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex)); this.name = name; this.len = len; if (!len) return ERR_PTR(-EACCES); hash = init_name_hash(); while (len--) { c = *(const unsigned char *)name++; if (c == '/' || c == '\0') return ERR_PTR(-EACCES); hash = partial_name_hash(c, hash); } this.hash = end_name_hash(hash); /* * See if the low-level filesystem might want * to use its own hash.. */ if (base->d_flags & DCACHE_OP_HASH) { int err = base->d_op->d_hash(base, base->d_inode, &this); if (err < 0) return ERR_PTR(err); } return __lookup_hash(&this, base, NULL); } int user_path_at_empty(int dfd, const char __user *name, unsigned flags, struct path *path, int *empty) { struct nameidata nd; char *tmp = getname_flags(name, flags, empty); int err = PTR_ERR(tmp); if (!IS_ERR(tmp)) { BUG_ON(flags & LOOKUP_PARENT); err = do_path_lookup(dfd, tmp, flags, &nd); putname(tmp); if (!err) *path = nd.path; } return err; } int user_path_at(int dfd, const char __user *name, unsigned flags, struct path *path) { return user_path_at_empty(dfd, name, flags, path, 0); } static int user_path_parent(int dfd, const char __user *path, struct nameidata *nd, char **name) { char *s = getname(path); int error; if (IS_ERR(s)) return PTR_ERR(s); error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd); if (error) putname(s); else *name = s; return error; } /* * It's inline, so penalty for filesystems that don't use sticky bit is * minimal. */ static inline int check_sticky(struct inode *dir, struct inode *inode) { uid_t fsuid = current_fsuid(); if (!(dir->i_mode & S_ISVTX)) return 0; if (current_user_ns() != inode_userns(inode)) goto other_userns; if (inode->i_uid == fsuid) return 0; if (dir->i_uid == fsuid) return 0; other_userns: return !ns_capable(inode_userns(inode), CAP_FOWNER); } /* * Check whether we can remove a link victim from directory dir, check * whether the type of victim is right. * 1. We can't do it if dir is read-only (done in permission()) * 2. We should have write and exec permissions on dir * 3. We can't remove anything from append-only dir * 4. We can't do anything with immutable dir (done in permission()) * 5. If the sticky bit on dir is set we should either * a. be owner of dir, or * b. be owner of victim, or * c. have CAP_FOWNER capability * 6. If the victim is append-only or immutable we can't do antyhing with * links pointing to it. * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. * 9. We can't remove a root or mountpoint. * 10. We don't allow removal of NFS sillyrenamed files; it's handled by * nfs_async_unlink(). */ static int may_delete(struct inode *dir,struct dentry *victim,int isdir) { int error; if (!victim->d_inode) return -ENOENT; BUG_ON(victim->d_parent->d_inode != dir); audit_inode_child(victim, dir); error = inode_permission(dir, MAY_WRITE | MAY_EXEC); if (error) return error; if (IS_APPEND(dir)) return -EPERM; if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)|| IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode)) return -EPERM; if (isdir) { if (!S_ISDIR(victim->d_inode->i_mode)) return -ENOTDIR; if (IS_ROOT(victim)) return -EBUSY; } else if (S_ISDIR(victim->d_inode->i_mode)) return -EISDIR; if (IS_DEADDIR(dir)) return -ENOENT; if (victim->d_flags & DCACHE_NFSFS_RENAMED) return -EBUSY; return 0; } /* Check whether we can create an object with dentry child in directory * dir. * 1. We can't do it if child already exists (open has special treatment for * this case, but since we are inlined it's OK) * 2. We can't do it if dir is read-only (done in permission()) * 3. We should have write and exec permissions on dir * 4. We can't do it if dir is immutable (done in permission()) */ static inline int may_create(struct inode *dir, struct dentry *child) { if (child->d_inode) return -EEXIST; if (IS_DEADDIR(dir)) return -ENOENT; return inode_permission(dir, MAY_WRITE | MAY_EXEC); } /* * p1 and p2 should be directories on the same fs. */ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) { struct dentry *p; if (p1 == p2) { mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); return NULL; } mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex); p = d_ancestor(p2, p1); if (p) { mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT); mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD); return p; } p = d_ancestor(p1, p2); if (p) { mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); return p; } mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); return NULL; } void unlock_rename(struct dentry *p1, struct dentry *p2) { mutex_unlock(&p1->d_inode->i_mutex); if (p1 != p2) { mutex_unlock(&p2->d_inode->i_mutex); mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex); } } int vfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd) { int error = may_create(dir, dentry); if (error) return error; if (!dir->i_op->create) return -EACCES; /* shouldn't it be ENOSYS? */ mode &= S_IALLUGO; mode |= S_IFREG; error = security_inode_create(dir, dentry, mode); if (error) return error; error = dir->i_op->create(dir, dentry, mode, nd); if (!error) fsnotify_create(dir, dentry); return error; } static int may_open(struct path *path, int acc_mode, int flag) { struct dentry *dentry = path->dentry; struct inode *inode = dentry->d_inode; int error; /* O_PATH? */ if (!acc_mode) return 0; if (!inode) return -ENOENT; switch (inode->i_mode & S_IFMT) { case S_IFLNK: return -ELOOP; case S_IFDIR: if (acc_mode & MAY_WRITE) return -EISDIR; break; case S_IFBLK: case S_IFCHR: if (path->mnt->mnt_flags & MNT_NODEV) return -EACCES; /*FALLTHRU*/ case S_IFIFO: case S_IFSOCK: flag &= ~O_TRUNC; break; } error = inode_permission(inode, acc_mode); if (error) return error; /* * An append-only file must be opened in append mode for writing. */ if (IS_APPEND(inode)) { if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) return -EPERM; if (flag & O_TRUNC) return -EPERM; } /* O_NOATIME can only be set by the owner or superuser */ if (flag & O_NOATIME && !inode_owner_or_capable(inode)) return -EPERM; return 0; } static int handle_truncate(struct file *filp) { struct path *path = &filp->f_path; struct inode *inode = path->dentry->d_inode; int error = get_write_access(inode); if (error) return error; /* * Refuse to truncate files with mandatory locks held on them. */ error = locks_verify_locked(inode); if (!error) error = security_path_truncate(path); if (!error) { error = do_truncate(path->dentry, 0, ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, filp); } put_write_access(inode); return error; } static inline int open_to_namei_flags(int flag) { if ((flag & O_ACCMODE) == 3) flag--; return flag; } /* * Handle the last step of open() */ static struct file *do_last(struct nameidata *nd, struct path *path, const struct open_flags *op, const char *pathname) { struct dentry *dir = nd->path.dentry; struct dentry *dentry; int open_flag = op->open_flag; int will_truncate = open_flag & O_TRUNC; int want_write = 0; int acc_mode = op->acc_mode; struct file *filp; int error; nd->flags &= ~LOOKUP_PARENT; nd->flags |= op->intent; switch (nd->last_type) { case LAST_DOTDOT: case LAST_DOT: error = handle_dots(nd, nd->last_type); if (error) return ERR_PTR(error); /* fallthrough */ case LAST_ROOT: error = complete_walk(nd); if (error) return ERR_PTR(error); audit_inode(pathname, nd->path.dentry); if (open_flag & O_CREAT) { error = -EISDIR; goto exit; } goto ok; case LAST_BIND: error = complete_walk(nd); if (error) return ERR_PTR(error); audit_inode(pathname, dir); goto ok; } if (!(open_flag & O_CREAT)) { int symlink_ok = 0; if (nd->last.name[nd->last.len]) nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW)) symlink_ok = 1; /* we _can_ be in RCU mode here */ error = walk_component(nd, path, &nd->last, LAST_NORM, !symlink_ok); if (error < 0) return ERR_PTR(error); if (error) /* symlink */ return NULL; /* sayonara */ error = complete_walk(nd); if (error) return ERR_PTR(-ECHILD); error = -ENOTDIR; if (nd->flags & LOOKUP_DIRECTORY) { if (!nd->inode->i_op->lookup) goto exit; } audit_inode(pathname, nd->path.dentry); goto ok; } /* create side of things */ /* * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been * cleared when we got to the last component we are about to look up */ error = complete_walk(nd); if (error) return ERR_PTR(error); audit_inode(pathname, dir); error = -EISDIR; /* trailing slashes? */ if (nd->last.name[nd->last.len]) goto exit; mutex_lock(&dir->d_inode->i_mutex); dentry = lookup_hash(nd); error = PTR_ERR(dentry); if (IS_ERR(dentry)) { mutex_unlock(&dir->d_inode->i_mutex); goto exit; } path->dentry = dentry; path->mnt = nd->path.mnt; /* Negative dentry, just create the file */ if (!dentry->d_inode) { int mode = op->mode; if (!IS_POSIXACL(dir->d_inode)) mode &= ~current_umask(); /* * This write is needed to ensure that a * rw->ro transition does not occur between * the time when the file is created and when * a permanent write count is taken through * the 'struct file' in nameidata_to_filp(). */ error = mnt_want_write(nd->path.mnt); if (error) goto exit_mutex_unlock; want_write = 1; /* Don't check for write permission, don't truncate */ open_flag &= ~O_TRUNC; will_truncate = 0; acc_mode = MAY_OPEN; error = security_path_mknod(&nd->path, dentry, mode, 0); if (error) goto exit_mutex_unlock; error = vfs_create(dir->d_inode, dentry, mode, nd); if (error) goto exit_mutex_unlock; mutex_unlock(&dir->d_inode->i_mutex); dput(nd->path.dentry); nd->path.dentry = dentry; goto common; } /* * It already exists. */ mutex_unlock(&dir->d_inode->i_mutex); audit_inode(pathname, path->dentry); error = -EEXIST; if (open_flag & O_EXCL) goto exit_dput; error = follow_managed(path, nd->flags); if (error < 0) goto exit_dput; if (error) nd->flags |= LOOKUP_JUMPED; error = -ENOENT; if (!path->dentry->d_inode) goto exit_dput; if (path->dentry->d_inode->i_op->follow_link) return NULL; path_to_nameidata(path, nd); nd->inode = path->dentry->d_inode; /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ error = complete_walk(nd); if (error) goto exit; error = -EISDIR; if (S_ISDIR(nd->inode->i_mode)) goto exit; ok: if (!S_ISREG(nd->inode->i_mode)) will_truncate = 0; if (will_truncate) { error = mnt_want_write(nd->path.mnt); if (error) goto exit; want_write = 1; } common: error = may_open(&nd->path, acc_mode, open_flag); if (error) goto exit; filp = nameidata_to_filp(nd); if (!IS_ERR(filp)) { error = ima_file_check(filp, op->acc_mode); if (error) { fput(filp); filp = ERR_PTR(error); } } if (!IS_ERR(filp)) { if (will_truncate) { error = handle_truncate(filp); if (error) { fput(filp); filp = ERR_PTR(error); } } } out: if (want_write) mnt_drop_write(nd->path.mnt); path_put(&nd->path); return filp; exit_mutex_unlock: mutex_unlock(&dir->d_inode->i_mutex); exit_dput: path_put_conditional(path, nd); exit: filp = ERR_PTR(error); goto out; } static struct file *path_openat(int dfd, const char *pathname, struct nameidata *nd, const struct open_flags *op, int flags) { struct file *base = NULL; struct file *filp; struct path path; int error; filp = get_empty_filp(); if (!filp) return ERR_PTR(-ENFILE); filp->f_flags = op->open_flag; nd->intent.open.file = filp; nd->intent.open.flags = open_to_namei_flags(op->open_flag); nd->intent.open.create_mode = op->mode; error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base); if (unlikely(error)) goto out_filp; current->total_link_count = 0; error = link_path_walk(pathname, nd); if (unlikely(error)) goto out_filp; filp = do_last(nd, &path, op, pathname); while (unlikely(!filp)) { /* trailing symlink */ struct path link = path; void *cookie; if (!(nd->flags & LOOKUP_FOLLOW)) { path_put_conditional(&path, nd); path_put(&nd->path); filp = ERR_PTR(-ELOOP); break; } nd->flags |= LOOKUP_PARENT; nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); error = follow_link(&link, nd, &cookie); if (unlikely(error)) filp = ERR_PTR(error); else filp = do_last(nd, &path, op, pathname); put_link(nd, &link, cookie); } out: if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) path_put(&nd->root); if (base) fput(base); release_open_intent(nd); return filp; out_filp: filp = ERR_PTR(error); goto out; } struct file *do_filp_open(int dfd, const char *pathname, const struct open_flags *op, int flags) { struct nameidata nd; struct file *filp; filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU); if (unlikely(filp == ERR_PTR(-ECHILD))) filp = path_openat(dfd, pathname, &nd, op, flags); if (unlikely(filp == ERR_PTR(-ESTALE))) filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL); return filp; } struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, const char *name, const struct open_flags *op, int flags) { struct nameidata nd; struct file *file; nd.root.mnt = mnt; nd.root.dentry = dentry; flags |= LOOKUP_ROOT; if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN) return ERR_PTR(-ELOOP); file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU); if (unlikely(file == ERR_PTR(-ECHILD))) file = path_openat(-1, name, &nd, op, flags); if (unlikely(file == ERR_PTR(-ESTALE))) file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL); return file; } struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir) { struct dentry *dentry = ERR_PTR(-EEXIST); struct nameidata nd; int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd); if (error) return ERR_PTR(error); /* * Yucky last component or no last component at all? * (foo/., foo/.., /////) */ if (nd.last_type != LAST_NORM) goto out; nd.flags &= ~LOOKUP_PARENT; nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL; nd.intent.open.flags = O_EXCL; /* * Do the final lookup. */ mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); dentry = lookup_hash(&nd); if (IS_ERR(dentry)) goto fail; if (dentry->d_inode) goto eexist; /* * Special case - lookup gave negative, but... we had foo/bar/ * From the vfs_mknod() POV we just have a negative dentry - * all is fine. Let's be bastards - you had / on the end, you've * been asking for (non-existent) directory. -ENOENT for you. */ if (unlikely(!is_dir && nd.last.name[nd.last.len])) { dput(dentry); dentry = ERR_PTR(-ENOENT); goto fail; } *path = nd.path; return dentry; eexist: dput(dentry); dentry = ERR_PTR(-EEXIST); fail: mutex_unlock(&nd.path.dentry->d_inode->i_mutex); out: path_put(&nd.path); return dentry; } EXPORT_SYMBOL(kern_path_create); struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir) { char *tmp = getname(pathname); struct dentry *res; if (IS_ERR(tmp)) return ERR_CAST(tmp); res = kern_path_create(dfd, tmp, path, is_dir); putname(tmp); return res; } EXPORT_SYMBOL(user_path_create); int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev) { int error = may_create(dir, dentry); if (error) return error; if ((S_ISCHR(mode) || S_ISBLK(mode)) && !ns_capable(inode_userns(dir), CAP_MKNOD)) return -EPERM; if (!dir->i_op->mknod) return -EPERM; error = devcgroup_inode_mknod(mode, dev); if (error) return error; error = security_inode_mknod(dir, dentry, mode, dev); if (error) return error; error = dir->i_op->mknod(dir, dentry, mode, dev); if (!error) fsnotify_create(dir, dentry); return error; } static int may_mknod(mode_t mode) { switch (mode & S_IFMT) { case S_IFREG: case S_IFCHR: case S_IFBLK: case S_IFIFO: case S_IFSOCK: case 0: /* zero mode translates to S_IFREG */ return 0; case S_IFDIR: return -EPERM; default: return -EINVAL; } } SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode, unsigned, dev) { struct dentry *dentry; struct path path; int error; if (S_ISDIR(mode)) return -EPERM; dentry = user_path_create(dfd, filename, &path, 0); if (IS_ERR(dentry)) return PTR_ERR(dentry); if (!IS_POSIXACL(path.dentry->d_inode)) mode &= ~current_umask(); error = may_mknod(mode); if (error) goto out_dput; error = mnt_want_write(path.mnt); if (error) goto out_dput; error = security_path_mknod(&path, dentry, mode, dev); if (error) goto out_drop_write; switch (mode & S_IFMT) { case 0: case S_IFREG: error = vfs_create(path.dentry->d_inode,dentry,mode,NULL); break; case S_IFCHR: case S_IFBLK: error = vfs_mknod(path.dentry->d_inode,dentry,mode, new_decode_dev(dev)); break; case S_IFIFO: case S_IFSOCK: error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); break; } out_drop_write: mnt_drop_write(path.mnt); out_dput: dput(dentry); mutex_unlock(&path.dentry->d_inode->i_mutex); path_put(&path); return error; } SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev) { return sys_mknodat(AT_FDCWD, filename, mode, dev); } int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) { int error = may_create(dir, dentry); if (error) return error; if (!dir->i_op->mkdir) return -EPERM; mode &= (S_IRWXUGO|S_ISVTX); error = security_inode_mkdir(dir, dentry, mode); if (error) return error; error = dir->i_op->mkdir(dir, dentry, mode); if (!error) fsnotify_mkdir(dir, dentry); return error; } SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode) { struct dentry *dentry; struct path path; int error; dentry = user_path_create(dfd, pathname, &path, 1); if (IS_ERR(dentry)) return PTR_ERR(dentry); if (!IS_POSIXACL(path.dentry->d_inode)) mode &= ~current_umask(); error = mnt_want_write(path.mnt); if (error) goto out_dput; error = security_path_mkdir(&path, dentry, mode); if (error) goto out_drop_write; error = vfs_mkdir(path.dentry->d_inode, dentry, mode); out_drop_write: mnt_drop_write(path.mnt); out_dput: dput(dentry); mutex_unlock(&path.dentry->d_inode->i_mutex); path_put(&path); return error; } SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode) { return sys_mkdirat(AT_FDCWD, pathname, mode); } /* * The dentry_unhash() helper will try to drop the dentry early: we * should have a usage count of 2 if we're the only user of this * dentry, and if that is true (possibly after pruning the dcache), * then we drop the dentry now. * * A low-level filesystem can, if it choses, legally * do a * * if (!d_unhashed(dentry)) * return -EBUSY; * * if it cannot handle the case of removing a directory * that is still in use by something else.. */ void dentry_unhash(struct dentry *dentry) { shrink_dcache_parent(dentry); spin_lock(&dentry->d_lock); if (dentry->d_count == 1) __d_drop(dentry); spin_unlock(&dentry->d_lock); } int vfs_rmdir(struct inode *dir, struct dentry *dentry) { int error = may_delete(dir, dentry, 1); if (error) return error; if (!dir->i_op->rmdir) return -EPERM; dget(dentry); mutex_lock(&dentry->d_inode->i_mutex); error = -EBUSY; if (d_mountpoint(dentry)) goto out; error = security_inode_rmdir(dir, dentry); if (error) goto out; shrink_dcache_parent(dentry); error = dir->i_op->rmdir(dir, dentry); if (error) goto out; dentry->d_inode->i_flags |= S_DEAD; dont_mount(dentry); out: mutex_unlock(&dentry->d_inode->i_mutex); dput(dentry); if (!error) d_delete(dentry); return error; } static long do_rmdir(int dfd, const char __user *pathname) { int error = 0; char * name; struct dentry *dentry; struct nameidata nd; error = user_path_parent(dfd, pathname, &nd, &name); if (error) return error; switch(nd.last_type) { case LAST_DOTDOT: error = -ENOTEMPTY; goto exit1; case LAST_DOT: error = -EINVAL; goto exit1; case LAST_ROOT: error = -EBUSY; goto exit1; } nd.flags &= ~LOOKUP_PARENT; mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); dentry = lookup_hash(&nd); error = PTR_ERR(dentry); if (IS_ERR(dentry)) goto exit2; if (!dentry->d_inode) { error = -ENOENT; goto exit3; } error = mnt_want_write(nd.path.mnt); if (error) goto exit3; error = security_path_rmdir(&nd.path, dentry); if (error) goto exit4; error = vfs_rmdir(nd.path.dentry->d_inode, dentry); exit4: mnt_drop_write(nd.path.mnt); exit3: dput(dentry); exit2: mutex_unlock(&nd.path.dentry->d_inode->i_mutex); exit1: path_put(&nd.path); putname(name); return error; } SYSCALL_DEFINE1(rmdir, const char __user *, pathname) { return do_rmdir(AT_FDCWD, pathname); } int vfs_unlink(struct inode *dir, struct dentry *dentry) { int error = may_delete(dir, dentry, 0); if (error) return error; if (!dir->i_op->unlink) return -EPERM; mutex_lock(&dentry->d_inode->i_mutex); if (d_mountpoint(dentry)) error = -EBUSY; else { error = security_inode_unlink(dir, dentry); if (!error) { error = dir->i_op->unlink(dir, dentry); if (!error) dont_mount(dentry); } } mutex_unlock(&dentry->d_inode->i_mutex); /* We don't d_delete() NFS sillyrenamed files--they still exist. */ if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { fsnotify_link_count(dentry->d_inode); d_delete(dentry); } return error; } /* * Make sure that the actual truncation of the file will occur outside its * directory's i_mutex. Truncate can take a long time if there is a lot of * writeout happening, and we don't want to prevent access to the directory * while waiting on the I/O. */ static long do_unlinkat(int dfd, const char __user *pathname) { int error; char *name; struct dentry *dentry; struct nameidata nd; struct inode *inode = NULL; error = user_path_parent(dfd, pathname, &nd, &name); if (error) return error; error = -EISDIR; if (nd.last_type != LAST_NORM) goto exit1; nd.flags &= ~LOOKUP_PARENT; mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); dentry = lookup_hash(&nd); error = PTR_ERR(dentry); if (!IS_ERR(dentry)) { /* Why not before? Because we want correct error value */ if (nd.last.name[nd.last.len]) goto slashes; inode = dentry->d_inode; if (!inode) goto slashes; ihold(inode); error = mnt_want_write(nd.path.mnt); if (error) goto exit2; error = security_path_unlink(&nd.path, dentry); if (error) goto exit3; error = vfs_unlink(nd.path.dentry->d_inode, dentry); exit3: mnt_drop_write(nd.path.mnt); exit2: dput(dentry); } mutex_unlock(&nd.path.dentry->d_inode->i_mutex); if (inode) iput(inode); /* truncate the inode here */ exit1: path_put(&nd.path); putname(name); return error; slashes: error = !dentry->d_inode ? -ENOENT : S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR; goto exit2; } SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) { if ((flag & ~AT_REMOVEDIR) != 0) return -EINVAL; if (flag & AT_REMOVEDIR) return do_rmdir(dfd, pathname); return do_unlinkat(dfd, pathname); } SYSCALL_DEFINE1(unlink, const char __user *, pathname) { return do_unlinkat(AT_FDCWD, pathname); } int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) { int error = may_create(dir, dentry); if (error) return error; if (!dir->i_op->symlink) return -EPERM; error = security_inode_symlink(dir, dentry, oldname); if (error) return error; error = dir->i_op->symlink(dir, dentry, oldname); if (!error) fsnotify_create(dir, dentry); return error; } SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, int, newdfd, const char __user *, newname) { int error; char *from; struct dentry *dentry; struct path path; from = getname(oldname); if (IS_ERR(from)) return PTR_ERR(from); dentry = user_path_create(newdfd, newname, &path, 0); error = PTR_ERR(dentry); if (IS_ERR(dentry)) goto out_putname; error = mnt_want_write(path.mnt); if (error) goto out_dput; error = security_path_symlink(&path, dentry, from); if (error) goto out_drop_write; error = vfs_symlink(path.dentry->d_inode, dentry, from); out_drop_write: mnt_drop_write(path.mnt); out_dput: dput(dentry); mutex_unlock(&path.dentry->d_inode->i_mutex); path_put(&path); out_putname: putname(from); return error; } SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) { return sys_symlinkat(oldname, AT_FDCWD, newname); } int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry) { struct inode *inode = old_dentry->d_inode; int error; if (!inode) return -ENOENT; error = may_create(dir, new_dentry); if (error) return error; if (dir->i_sb != inode->i_sb) return -EXDEV; /* * A link to an append-only or immutable file cannot be created. */ if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) return -EPERM; if (!dir->i_op->link) return -EPERM; if (S_ISDIR(inode->i_mode)) return -EPERM; error = security_inode_link(old_dentry, dir, new_dentry); if (error) return error; mutex_lock(&inode->i_mutex); /* Make sure we don't allow creating hardlink to an unlinked file */ if (inode->i_nlink == 0) error = -ENOENT; else error = dir->i_op->link(old_dentry, dir, new_dentry); mutex_unlock(&inode->i_mutex); if (!error) fsnotify_link(dir, inode, new_dentry); return error; } /* * Hardlinks are often used in delicate situations. We avoid * security-related surprises by not following symlinks on the * newname. --KAB * * We don't follow them on the oldname either to be compatible * with linux 2.0, and to avoid hard-linking to directories * and other special files. --ADM */ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, int, newdfd, const char __user *, newname, int, flags) { struct dentry *new_dentry; struct path old_path, new_path; int how = 0; int error; if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) return -EINVAL; /* * To use null names we require CAP_DAC_READ_SEARCH * This ensures that not everyone will be able to create * handlink using the passed filedescriptor. */ if (flags & AT_EMPTY_PATH) { if (!capable(CAP_DAC_READ_SEARCH)) return -ENOENT; how = LOOKUP_EMPTY; } if (flags & AT_SYMLINK_FOLLOW) how |= LOOKUP_FOLLOW; error = user_path_at(olddfd, oldname, how, &old_path); if (error) return error; new_dentry = user_path_create(newdfd, newname, &new_path, 0); error = PTR_ERR(new_dentry); if (IS_ERR(new_dentry)) goto out; error = -EXDEV; if (old_path.mnt != new_path.mnt) goto out_dput; error = mnt_want_write(new_path.mnt); if (error) goto out_dput; error = security_path_link(old_path.dentry, &new_path, new_dentry); if (error) goto out_drop_write; error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry); out_drop_write: mnt_drop_write(new_path.mnt); out_dput: dput(new_dentry); mutex_unlock(&new_path.dentry->d_inode->i_mutex); path_put(&new_path); out: path_put(&old_path); return error; } SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) { return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); } /* * The worst of all namespace operations - renaming directory. "Perverted" * doesn't even start to describe it. Somebody in UCB had a heck of a trip... * Problems: * a) we can get into loop creation. Check is done in is_subdir(). * b) race potential - two innocent renames can create a loop together. * That's where 4.4 screws up. Current fix: serialization on * sb->s_vfs_rename_mutex. We might be more accurate, but that's another * story. * c) we have to lock _three_ objects - parents and victim (if it exists). * And that - after we got ->i_mutex on parents (until then we don't know * whether the target exists). Solution: try to be smart with locking * order for inodes. We rely on the fact that tree topology may change * only under ->s_vfs_rename_mutex _and_ that parent of the object we * move will be locked. Thus we can rank directories by the tree * (ancestors first) and rank all non-directories after them. * That works since everybody except rename does "lock parent, lookup, * lock child" and rename is under ->s_vfs_rename_mutex. * HOWEVER, it relies on the assumption that any object with ->lookup() * has no more than 1 dentry. If "hybrid" objects will ever appear, * we'd better make sure that there's no link(2) for them. * d) conversion from fhandle to dentry may come in the wrong moment - when * we are removing the target. Solution: we will have to grab ->i_mutex * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on * ->i_mutex on parents, which works but leads to some truly excessive * locking]. */ static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) { int error = 0; struct inode *target = new_dentry->d_inode; /* * If we are going to change the parent - check write permissions, * we'll need to flip '..'. */ if (new_dir != old_dir) { error = inode_permission(old_dentry->d_inode, MAY_WRITE); if (error) return error; } error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); if (error) return error; dget(new_dentry); if (target) mutex_lock(&target->i_mutex); error = -EBUSY; if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry)) goto out; if (target) shrink_dcache_parent(new_dentry); error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); if (error) goto out; if (target) { target->i_flags |= S_DEAD; dont_mount(new_dentry); } out: if (target) mutex_unlock(&target->i_mutex); dput(new_dentry); if (!error) if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) d_move(old_dentry,new_dentry); return error; } static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) { struct inode *target = new_dentry->d_inode; int error; error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); if (error) return error; dget(new_dentry); if (target) mutex_lock(&target->i_mutex); error = -EBUSY; if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry)) goto out; error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); if (error) goto out; if (target) dont_mount(new_dentry); if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) d_move(old_dentry, new_dentry); out: if (target) mutex_unlock(&target->i_mutex); dput(new_dentry); return error; } int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) { int error; int is_dir = S_ISDIR(old_dentry->d_inode->i_mode); const unsigned char *old_name; if (old_dentry->d_inode == new_dentry->d_inode) return 0; error = may_delete(old_dir, old_dentry, is_dir); if (error) return error; if (!new_dentry->d_inode) error = may_create(new_dir, new_dentry); else error = may_delete(new_dir, new_dentry, is_dir); if (error) return error; if (!old_dir->i_op->rename) return -EPERM; old_name = fsnotify_oldname_init(old_dentry->d_name.name); if (is_dir) error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry); else error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry); if (!error) fsnotify_move(old_dir, new_dir, old_name, is_dir, new_dentry->d_inode, old_dentry); fsnotify_oldname_free(old_name); return error; } SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, int, newdfd, const char __user *, newname) { struct dentry *old_dir, *new_dir; struct dentry *old_dentry, *new_dentry; struct dentry *trap; struct nameidata oldnd, newnd; char *from; char *to; int error; error = user_path_parent(olddfd, oldname, &oldnd, &from); if (error) goto exit; error = user_path_parent(newdfd, newname, &newnd, &to); if (error) goto exit1; error = -EXDEV; if (oldnd.path.mnt != newnd.path.mnt) goto exit2; old_dir = oldnd.path.dentry; error = -EBUSY; if (oldnd.last_type != LAST_NORM) goto exit2; new_dir = newnd.path.dentry; if (newnd.last_type != LAST_NORM) goto exit2; oldnd.flags &= ~LOOKUP_PARENT; newnd.flags &= ~LOOKUP_PARENT; newnd.flags |= LOOKUP_RENAME_TARGET; trap = lock_rename(new_dir, old_dir); old_dentry = lookup_hash(&oldnd); error = PTR_ERR(old_dentry); if (IS_ERR(old_dentry)) goto exit3; /* source must exist */ error = -ENOENT; if (!old_dentry->d_inode) goto exit4; /* unless the source is a directory trailing slashes give -ENOTDIR */ if (!S_ISDIR(old_dentry->d_inode->i_mode)) { error = -ENOTDIR; if (oldnd.last.name[oldnd.last.len]) goto exit4; if (newnd.last.name[newnd.last.len]) goto exit4; } /* source should not be ancestor of target */ error = -EINVAL; if (old_dentry == trap) goto exit4; new_dentry = lookup_hash(&newnd); error = PTR_ERR(new_dentry); if (IS_ERR(new_dentry)) goto exit4; /* target should not be an ancestor of source */ error = -ENOTEMPTY; if (new_dentry == trap) goto exit5; error = mnt_want_write(oldnd.path.mnt); if (error) goto exit5; error = security_path_rename(&oldnd.path, old_dentry, &newnd.path, new_dentry); if (error) goto exit6; error = vfs_rename(old_dir->d_inode, old_dentry, new_dir->d_inode, new_dentry); exit6: mnt_drop_write(oldnd.path.mnt); exit5: dput(new_dentry); exit4: dput(old_dentry); exit3: unlock_rename(new_dir, old_dir); exit2: path_put(&newnd.path); putname(to); exit1: path_put(&oldnd.path); putname(from); exit: return error; } SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) { return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname); } int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link) { int len; len = PTR_ERR(link); if (IS_ERR(link)) goto out; len = strlen(link); if (len > (unsigned) buflen) len = buflen; if (copy_to_user(buffer, link, len)) len = -EFAULT; out: return len; } /* * A helper for ->readlink(). This should be used *ONLY* for symlinks that * have ->follow_link() touching nd only in nd_set_link(). Using (or not * using) it for any given inode is up to filesystem. */ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen) { struct nameidata nd; void *cookie; int res; nd.depth = 0; cookie = dentry->d_inode->i_op->follow_link(dentry, &nd); if (IS_ERR(cookie)) return PTR_ERR(cookie); res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd)); if (dentry->d_inode->i_op->put_link) dentry->d_inode->i_op->put_link(dentry, &nd, cookie); return res; } int vfs_follow_link(struct nameidata *nd, const char *link) { return __vfs_follow_link(nd, link); } /* get the link contents into pagecache */ static char *page_getlink(struct dentry * dentry, struct page **ppage) { char *kaddr; struct page *page; struct address_space *mapping = dentry->d_inode->i_mapping; page = read_mapping_page(mapping, 0, NULL); if (IS_ERR(page)) return (char*)page; *ppage = page; kaddr = kmap(page); nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1); return kaddr; } int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) { struct page *page = NULL; char *s = page_getlink(dentry, &page); int res = vfs_readlink(dentry,buffer,buflen,s); if (page) { kunmap(page); page_cache_release(page); } return res; } void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd) { struct page *page = NULL; nd_set_link(nd, page_getlink(dentry, &page)); return page; } void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) { struct page *page = cookie; if (page) { kunmap(page); page_cache_release(page); } } /* * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS */ int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) { struct address_space *mapping = inode->i_mapping; struct page *page; void *fsdata; int err; char *kaddr; unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; if (nofs) flags |= AOP_FLAG_NOFS; retry: err = pagecache_write_begin(NULL, mapping, 0, len-1, flags, &page, &fsdata); if (err) goto fail; kaddr = kmap_atomic(page, KM_USER0); memcpy(kaddr, symname, len-1); kunmap_atomic(kaddr, KM_USER0); err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, page, fsdata); if (err < 0) goto fail; if (err < len-1) goto retry; mark_inode_dirty(inode); return 0; fail: return err; } int page_symlink(struct inode *inode, const char *symname, int len) { return __page_symlink(inode, symname, len, !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS)); } const struct inode_operations page_symlink_inode_operations = { .readlink = generic_readlink, .follow_link = page_follow_link_light, .put_link = page_put_link, }; EXPORT_SYMBOL(user_path_at); EXPORT_SYMBOL(follow_down_one); EXPORT_SYMBOL(follow_down); EXPORT_SYMBOL(follow_up); EXPORT_SYMBOL(get_write_access); /* binfmt_aout */ EXPORT_SYMBOL(getname); EXPORT_SYMBOL(lock_rename); EXPORT_SYMBOL(lookup_one_len); EXPORT_SYMBOL(page_follow_link_light); EXPORT_SYMBOL(page_put_link); EXPORT_SYMBOL(page_readlink); EXPORT_SYMBOL(__page_symlink); EXPORT_SYMBOL(page_symlink); EXPORT_SYMBOL(page_symlink_inode_operations); EXPORT_SYMBOL(kern_path); EXPORT_SYMBOL(vfs_path_lookup); EXPORT_SYMBOL(inode_permission); EXPORT_SYMBOL(unlock_rename); EXPORT_SYMBOL(vfs_create); EXPORT_SYMBOL(vfs_follow_link); EXPORT_SYMBOL(vfs_link); EXPORT_SYMBOL(vfs_mkdir); EXPORT_SYMBOL(vfs_mknod); EXPORT_SYMBOL(generic_permission); EXPORT_SYMBOL(vfs_readlink); EXPORT_SYMBOL(vfs_rename); EXPORT_SYMBOL(vfs_rmdir); EXPORT_SYMBOL(vfs_symlink); EXPORT_SYMBOL(vfs_unlink); EXPORT_SYMBOL(dentry_unhash); EXPORT_SYMBOL(generic_readlink);