Commit e13b210f authored by Al Viro's avatar Al Viro Committed by Linus Torvalds
Browse files

[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
		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
		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 <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 463ffb2e
......@@ -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) {
*mnt = mounted;
*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) {
goto exit;
nd->mnt = path.mnt;
error = -ENOENT;
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