linux-kernel - [PATCH 5.10 021/188] LOOKUP_MOUNTPOINT: we are cleaning "jumped" flag too late

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Message-Id: <20210412084014.358736084@linuxfoundation.org>
Date:   Mon, 12 Apr 2021 10:38:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 5.10 021/188] LOOKUP_MOUNTPOINT: we are cleaning "jumped" flag too late

From: Al Viro <viro@...iv.linux.org.uk>

commit 4f0ed93fb92d3528c73c80317509df3f800a222b upstream.

That (and traversals in case of umount .) should be done before
complete_walk().  Either a braino or mismerge damage on queue
reorders - either way, I should've spotted that much earlier.

Fucked-up-by: Al Viro <viro@...iv.linux.org.uk>
X-Paperbag: Brown
Fixes: 161aff1d93ab "LOOKUP_MOUNTPOINT: fold path_mountpointat() into path_lookupat()"
Cc: stable@...r.kernel.org # v5.7+
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/namei.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2328,16 +2328,16 @@ static int path_lookupat(struct nameidat
 	while (!(err = link_path_walk(s, nd)) &&
 	       (s = lookup_last(nd)) != NULL)
 		;
+	if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
+		err = handle_lookup_down(nd);
+		nd->flags &= ~LOOKUP_JUMPED; // no d_weak_revalidate(), please...
+	}
 	if (!err)
 		err = complete_walk(nd);
 
 	if (!err && nd->flags & LOOKUP_DIRECTORY)
 		if (!d_can_lookup(nd->path.dentry))
 			err = -ENOTDIR;
-	if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
-		err = handle_lookup_down(nd);
-		nd->flags &= ~LOOKUP_JUMPED; // no d_weak_revalidate(), please...
-	}
 	if (!err) {
 		*path = nd->path;
 		nd->path.mnt = NULL;