Commit e13b210f authored Jun 06, 2005 by Al Viro Committed by Linus Torvalds Jun 06, 2005

[PATCH] namei fixes (10/19)



In open_namei(), __follow_down() loop turned into __follow_mount().
Instead of
	if we are on a mountpoint dentry
		if O_NOFOLLOW checks fail
			drop path.dentry
			drop nd
			return
		do equivalent of follow_mount(&path.mnt, &path.dentry)
		nd->mnt = path.mnt
we do
	if __follow_mount(path) had, indeed, traversed mountpoint
		/* now both nd->mnt and path.mnt are pinned down */
		if O_NOFOLLOW checks fail
			drop path.dentry
			drop path.mnt
			drop nd
			return
		mntput(nd->mnt)
		nd->mnt = path.mnt

Now __follow_down() can be folded into follow_down() - no other callers left.
We need to reorder dput()/mntput() there - same problem as in follow_mount().

Equivalent transformation + fix for a bug in O_NOFOLLOW handling - we used to
get -ELOOP if we had the same fs mounted on /foo and /bar, had something bound
on /bar/baz and tried to open /foo/baz with O_NOFOLLOW.  And fix of
too-early-mntput() race in follow_down()

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 463ffb2e

fs/namei.c

+9 −11

Original line number	Diff line number	Diff line
		@@ -612,26 +612,21 @@ static int follow_mount(struct vfsmount mnt, struct dentry dentry)
		/* no need for dcache_lock, as serialization is taken care in
		* namespace.c
		*/
		static inline int __follow_down(struct vfsmount mnt, struct dentry dentry)
		int follow_down(struct vfsmount mnt, struct dentry dentry)
		{
		struct vfsmount *mounted;

		mounted = lookup_mnt(mnt, dentry);
		if (mounted) {
		dput(*dentry);
		mntput(*mnt);
		*mnt = mounted;
		dput(*dentry);
		*dentry = dget(mounted->mnt_root);
		return 1;
		}
		return 0;
		}

		int follow_down(struct vfsmount mnt, struct dentry dentry)
		{
		return __follow_down(mnt,dentry);
		}

		static inline void follow_dotdot(struct vfsmount mnt, struct dentry dentry)
		{
		while(1) {
		@@ -1498,11 +1493,14 @@ do_last:
		if (flag & O_EXCL)
		goto exit_dput;

		if (d_mountpoint(path.dentry)) {
		if (__follow_mount(&path)) {
		error = -ELOOP;
		if (flag & O_NOFOLLOW)
		goto exit_dput;
		while (__follow_down(&path.mnt,&path.dentry) && d_mountpoint(path.dentry));
		if (flag & O_NOFOLLOW) {
		dput(path.dentry);
		mntput(path.mnt);
		goto exit;
		}
		mntput(nd->mnt);
		nd->mnt = path.mnt;
		}
		error = -ENOENT;

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