linux_dsm_epyc7002/fs/kernfs/inode.c
Ondrej Mosnacek 1537ad15c9 kernfs: fix xattr name handling in LSM helpers
The implementation of kernfs_security_xattr_*() helpers reuses the
kernfs_node_xattr_*() functions, which take the suffix of the xattr name
and extract full xattr name from it using xattr_full_name(). However,
this function relies on the fact that the suffix passed to xattr
handlers from VFS is always constructed from the full name by just
incerementing the pointer. This doesn't necessarily hold for the callers
of kernfs_security_xattr_*(), so their usage will easily lead to
out-of-bounds access.

Fix this by moving the xattr name reconstruction to the VFS xattr
handlers and replacing the kernfs_security_xattr_*() helpers with more
general kernfs_xattr_*() helpers that take full xattr name and allow
accessing all kernfs node's xattrs.

Reported-by: kernel test robot <rong.a.chen@intel.com>
Fixes: b230d5aba2 ("LSM: add new hook for kernfs node initialization")
Fixes: ec882da5cd ("selinux: implement the kernfs_init_security hook")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2019-04-04 09:00:27 -04:00

349 lines
8.4 KiB
C

/*
* fs/kernfs/inode.c - kernfs inode implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
*
* This file is released under the GPLv2.
*/
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include "kernfs-internal.h"
static const struct address_space_operations kernfs_aops = {
.readpage = simple_readpage,
.write_begin = simple_write_begin,
.write_end = simple_write_end,
};
static const struct inode_operations kernfs_iops = {
.permission = kernfs_iop_permission,
.setattr = kernfs_iop_setattr,
.getattr = kernfs_iop_getattr,
.listxattr = kernfs_iop_listxattr,
};
static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
{
static DEFINE_MUTEX(iattr_mutex);
struct kernfs_iattrs *ret;
mutex_lock(&iattr_mutex);
if (kn->iattr || !alloc)
goto out_unlock;
kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
if (!kn->iattr)
goto out_unlock;
/* assign default attributes */
kn->iattr->ia_uid = GLOBAL_ROOT_UID;
kn->iattr->ia_gid = GLOBAL_ROOT_GID;
ktime_get_real_ts64(&kn->iattr->ia_atime);
kn->iattr->ia_mtime = kn->iattr->ia_atime;
kn->iattr->ia_ctime = kn->iattr->ia_atime;
simple_xattrs_init(&kn->iattr->xattrs);
out_unlock:
ret = kn->iattr;
mutex_unlock(&iattr_mutex);
return ret;
}
static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
{
return __kernfs_iattrs(kn, 1);
}
static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
{
return __kernfs_iattrs(kn, 0);
}
int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
{
struct kernfs_iattrs *attrs;
unsigned int ia_valid = iattr->ia_valid;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
if (ia_valid & ATTR_UID)
attrs->ia_uid = iattr->ia_uid;
if (ia_valid & ATTR_GID)
attrs->ia_gid = iattr->ia_gid;
if (ia_valid & ATTR_ATIME)
attrs->ia_atime = iattr->ia_atime;
if (ia_valid & ATTR_MTIME)
attrs->ia_mtime = iattr->ia_mtime;
if (ia_valid & ATTR_CTIME)
attrs->ia_ctime = iattr->ia_ctime;
if (ia_valid & ATTR_MODE)
kn->mode = iattr->ia_mode;
return 0;
}
/**
* kernfs_setattr - set iattr on a node
* @kn: target node
* @iattr: iattr to set
*
* Returns 0 on success, -errno on failure.
*/
int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
{
int ret;
mutex_lock(&kernfs_mutex);
ret = __kernfs_setattr(kn, iattr);
mutex_unlock(&kernfs_mutex);
return ret;
}
int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
{
struct inode *inode = d_inode(dentry);
struct kernfs_node *kn = inode->i_private;
int error;
if (!kn)
return -EINVAL;
mutex_lock(&kernfs_mutex);
error = setattr_prepare(dentry, iattr);
if (error)
goto out;
error = __kernfs_setattr(kn, iattr);
if (error)
goto out;
/* this ignores size changes */
setattr_copy(inode, iattr);
out:
mutex_unlock(&kernfs_mutex);
return error;
}
ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
{
struct kernfs_node *kn = kernfs_dentry_node(dentry);
struct kernfs_iattrs *attrs;
attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
}
static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
{
inode->i_mode = mode;
inode->i_atime = inode->i_mtime =
inode->i_ctime = current_time(inode);
}
static inline void set_inode_attr(struct inode *inode,
struct kernfs_iattrs *attrs)
{
struct super_block *sb = inode->i_sb;
inode->i_uid = attrs->ia_uid;
inode->i_gid = attrs->ia_gid;
inode->i_atime = timespec64_trunc(attrs->ia_atime, sb->s_time_gran);
inode->i_mtime = timespec64_trunc(attrs->ia_mtime, sb->s_time_gran);
inode->i_ctime = timespec64_trunc(attrs->ia_ctime, sb->s_time_gran);
}
static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
{
struct kernfs_iattrs *attrs = kn->iattr;
inode->i_mode = kn->mode;
if (attrs)
/*
* kernfs_node has non-default attributes get them from
* persistent copy in kernfs_node.
*/
set_inode_attr(inode, attrs);
if (kernfs_type(kn) == KERNFS_DIR)
set_nlink(inode, kn->dir.subdirs + 2);
}
int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
struct inode *inode = d_inode(path->dentry);
struct kernfs_node *kn = inode->i_private;
mutex_lock(&kernfs_mutex);
kernfs_refresh_inode(kn, inode);
mutex_unlock(&kernfs_mutex);
generic_fillattr(inode, stat);
return 0;
}
static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
{
kernfs_get(kn);
inode->i_private = kn;
inode->i_mapping->a_ops = &kernfs_aops;
inode->i_op = &kernfs_iops;
inode->i_generation = kn->id.generation;
set_default_inode_attr(inode, kn->mode);
kernfs_refresh_inode(kn, inode);
/* initialize inode according to type */
switch (kernfs_type(kn)) {
case KERNFS_DIR:
inode->i_op = &kernfs_dir_iops;
inode->i_fop = &kernfs_dir_fops;
if (kn->flags & KERNFS_EMPTY_DIR)
make_empty_dir_inode(inode);
break;
case KERNFS_FILE:
inode->i_size = kn->attr.size;
inode->i_fop = &kernfs_file_fops;
break;
case KERNFS_LINK:
inode->i_op = &kernfs_symlink_iops;
break;
default:
BUG();
}
unlock_new_inode(inode);
}
/**
* kernfs_get_inode - get inode for kernfs_node
* @sb: super block
* @kn: kernfs_node to allocate inode for
*
* Get inode for @kn. If such inode doesn't exist, a new inode is
* allocated and basics are initialized. New inode is returned
* locked.
*
* LOCKING:
* Kernel thread context (may sleep).
*
* RETURNS:
* Pointer to allocated inode on success, NULL on failure.
*/
struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
{
struct inode *inode;
inode = iget_locked(sb, kn->id.ino);
if (inode && (inode->i_state & I_NEW))
kernfs_init_inode(kn, inode);
return inode;
}
/*
* The kernfs_node serves as both an inode and a directory entry for
* kernfs. To prevent the kernfs inode numbers from being freed
* prematurely we take a reference to kernfs_node from the kernfs inode. A
* super_operations.evict_inode() implementation is needed to drop that
* reference upon inode destruction.
*/
void kernfs_evict_inode(struct inode *inode)
{
struct kernfs_node *kn = inode->i_private;
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
kernfs_put(kn);
}
int kernfs_iop_permission(struct inode *inode, int mask)
{
struct kernfs_node *kn;
if (mask & MAY_NOT_BLOCK)
return -ECHILD;
kn = inode->i_private;
mutex_lock(&kernfs_mutex);
kernfs_refresh_inode(kn, inode);
mutex_unlock(&kernfs_mutex);
return generic_permission(inode, mask);
}
int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
void *value, size_t size)
{
struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
if (!attrs)
return -ENODATA;
return simple_xattr_get(&attrs->xattrs, name, value, size);
}
int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
const void *value, size_t size, int flags)
{
struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
}
static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
struct dentry *unused, struct inode *inode,
const char *suffix, void *value, size_t size)
{
const char *name = xattr_full_name(handler, suffix);
struct kernfs_node *kn = inode->i_private;
return kernfs_xattr_get(kn, name, value, size);
}
static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
struct dentry *unused, struct inode *inode,
const char *suffix, const void *value,
size_t size, int flags)
{
const char *name = xattr_full_name(handler, suffix);
struct kernfs_node *kn = inode->i_private;
return kernfs_xattr_set(kn, name, value, size, flags);
}
static const struct xattr_handler kernfs_trusted_xattr_handler = {
.prefix = XATTR_TRUSTED_PREFIX,
.get = kernfs_vfs_xattr_get,
.set = kernfs_vfs_xattr_set,
};
static const struct xattr_handler kernfs_security_xattr_handler = {
.prefix = XATTR_SECURITY_PREFIX,
.get = kernfs_vfs_xattr_get,
.set = kernfs_vfs_xattr_set,
};
const struct xattr_handler *kernfs_xattr_handlers[] = {
&kernfs_trusted_xattr_handler,
&kernfs_security_xattr_handler,
NULL
};