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Commit e13b210f authored by Al Viro's avatar Al Viro Committed by Linus Torvalds
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[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: default avatarAl Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus 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 @@ int open_namei(const char * pathname, int flag, int mode, struct nameidata *nd) 
	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;