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fix execute checking in permission()

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permission() checks that MAY_EXEC is only allowed on regular files if at least
one execute bit is set in the file mode.

generic_permission() already ensures this, so the extra check in permission()
is superfluous.

If the filesystem defines it's own ->permission() the check may still be
needed.  In this case move it after ->permission().  This is needed because
filesystems such as FUSE may need to refresh the inode attributes before
checking permissions.

This check should be moved inside ->permission(), but that's another story.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Miklos Szeredi 2007-10-16 23:27:08 -07:00 committed by Linus Torvalds
parent 043f46f615
commit 22590e41cb
1 changed files with 24 additions and 12 deletions
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36
fs/namei.c
View file

@ -227,10 +227,10 @@ int generic_permission(struct inode *inode, int mask,
int permission(struct inode *inode, int mask, struct nameidata *nd)
{
umode_t mode = inode->i_mode;
int retval, submask;
if (mask & MAY_WRITE) {
umode_t mode = inode->i_mode;
/*
* Nobody gets write access to a read-only fs.
@ -246,22 +246,34 @@ int permission(struct inode *inode, int mask, struct nameidata *nd)
return -EACCES;
}
/*
* MAY_EXEC on regular files requires special handling: We override
* filesystem execute permissions if the mode bits aren't set or
* the fs is mounted with the "noexec" flag.
*/
if ((mask & MAY_EXEC) && S_ISREG(mode) && (!(mode & S_IXUGO) ||
(nd && nd->mnt && (nd->mnt->mnt_flags & MNT_NOEXEC))))
return -EACCES;
if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) {
/*
* MAY_EXEC on regular files is denied if the fs is mounted
* with the "noexec" flag.
*/
if (nd && nd->mnt && (nd->mnt->mnt_flags & MNT_NOEXEC))
return -EACCES;
}
/* Ordinary permission routines do not understand MAY_APPEND. */
submask = mask & ~MAY_APPEND;
if (inode->i_op && inode->i_op->permission)
if (inode->i_op && inode->i_op->permission) {
retval = inode->i_op->permission(inode, submask, nd);
else
if (!retval) {
/*
* Exec permission on a regular file is denied if none
* of the execute bits are set.
*
* This check should be done by the ->permission()
* method.
*/
if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode) &&
!(inode->i_mode & S_IXUGO))
return -EACCES;
}
} else {
retval = generic_permission(inode, submask, NULL);
}
if (retval)
return retval;