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Make 'check_acl()' a first-class filesystem op

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This is stage one in flattening out the callchains for the common
permission testing.  Rather than have most filesystem implement their
own inode->i_op->permission function that just calls back down to the
VFS layers 'generic_permission()' with the per-filesystem ACL checking
function, the filesystem can just expose its 'check_acl' function
directly, and let the VFS layer do everything for it.

This is all just preparatory - no filesystem actually enables this yet.

Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2009-08-28 11:51:25 -07:00
parent cb9179ead0
commit 5909ccaa30
2 changed files with 42 additions and 33 deletions
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74
fs/namei.c
View File

@ -169,6 +169,36 @@ void putname(const char *name)
EXPORT_SYMBOL(putname);
#endif
/*
* This does basic POSIX ACL permission checking
*/
static int acl_permission_check(struct inode *inode, int mask,
int (*check_acl)(struct inode *inode, int mask))
{
umode_t mode = inode->i_mode;
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (current_fsuid() == inode->i_uid)
mode >>= 6;
else {
if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
int error = check_acl(inode, mask);
if (error != -EAGAIN)
return error;
}
if (in_group_p(inode->i_gid))
mode >>= 3;
}
/*
* If the DACs are ok we don't need any capability check.
*/
if ((mask & ~mode) == 0)
return 0;
return -EACCES;
}
/**
* generic_permission - check for access rights on a Posix-like filesystem
@ -184,32 +214,15 @@ EXPORT_SYMBOL(putname);
int generic_permission(struct inode *inode, int mask,
int (*check_acl)(struct inode *inode, int mask))
{
umode_t mode = inode->i_mode;
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (current_fsuid() == inode->i_uid)
mode >>= 6;
else {
if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
int error = check_acl(inode, mask);
if (error == -EACCES)
goto check_capabilities;
else if (error != -EAGAIN)
return error;
}
if (in_group_p(inode->i_gid))
mode >>= 3;
}
int ret;
/*
* If the DACs are ok we don't need any capability check.
* Do the basic POSIX ACL permission checks.
*/
if ((mask & ~mode) == 0)
return 0;
ret = acl_permission_check(inode, mask, check_acl);
if (ret != -EACCES)
return ret;
check_capabilities:
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable if at least one exec bit is set.
@ -262,7 +275,7 @@ int inode_permission(struct inode *inode, int mask)
if (inode->i_op->permission)
retval = inode->i_op->permission(inode, mask);
else
retval = generic_permission(inode, mask, NULL);
retval = generic_permission(inode, mask, inode->i_op->check_acl);
if (retval)
return retval;
@ -432,27 +445,22 @@ static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name,
*/
static int exec_permission_lite(struct inode *inode)
{
umode_t mode = inode->i_mode;
int ret;
if (inode->i_op->permission) {
int ret = inode->i_op->permission(inode, MAY_EXEC);
ret = inode->i_op->permission(inode, MAY_EXEC);
if (!ret)
goto ok;
return ret;
}
if (current_fsuid() == inode->i_uid)
mode >>= 6;
else if (in_group_p(inode->i_gid))
mode >>= 3;
if (mode & MAY_EXEC)
ret = acl_permission_check(inode, MAY_EXEC, inode->i_op->check_acl);
if (!ret)
goto ok;
if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
goto ok;
return -EACCES;
return ret;
ok:
return security_inode_permission(inode, MAY_EXEC);
}

1
include/linux/fs.h
View File

@ -1528,6 +1528,7 @@ struct inode_operations {
void (*put_link) (struct dentry *, struct nameidata *, void *);
void (*truncate) (struct inode *);
int (*permission) (struct inode *, int);
int (*check_acl)(struct inode *, int);
int (*setattr) (struct dentry *, struct iattr *);
int (*getattr) (struct vfsmount *mnt, struct dentry *, struct kstat *);
int (*setxattr) (struct dentry *, const char *,const void *,size_t,int);