linux-kernel - [040/165] VFS: move BUG_ON test for symlink nd->depth after

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Message-Id: <20110601081112.745416977@blue.kroah.org>
Date:	Wed, 01 Jun 2011 17:10:10 +0900
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Erez Zadok <ezk@...sunysb.edu>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [040/165] VFS: move BUG_ON test for symlink nd->depth after

2.6.39-stable review patch.  If anyone has any objections, please let us know.

------------------
 current->link_count test
Content-Length: 1009
Lines: 37

From: Erez Zadok <ezk@....cs.sunysb.edu>

commit 1a4022f88d40e1255920b017556092ab926d7f66 upstream.

This solves a serious VFS-level bug in nested_symlink (which was
rewritten from do_follow_link), and follows the order of depth tests
that existed before.

The bug triggers a BUG_ON in fs/namei.c:1381, when running racer with
symlink and rename ops.

Signed-off-by: Erez Zadok <ezk@...sunysb.edu>
Acked-by: Miklos Szeredi <mszeredi@...e.cz>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/namei.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1378,12 +1378,12 @@ static inline int nested_symlink(struct
 {
 	int res;
 
-	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
 	if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
 		path_put_conditional(path, nd);
 		path_put(&nd->path);
 		return -ELOOP;
 	}
+	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
 
 	nd->depth++;
 	current->link_count++;


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