linux-kernel - [053/103] ocfs2: Dont walk off the end of fast symlinks.

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Message-Id: <20101022185232.104229888@clark.site>
Date:	Fri, 22 Oct 2010 11:51:27 -0700
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,
	Joel Becker <joel.becker@...cle.com>
Subject: [053/103] ocfs2: Dont walk off the end of fast symlinks.

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

------------------

From: Joel Becker <joel.becker@...cle.com>

commit 1fc8a117865b54590acd773a55fbac9221b018f0 upstream.

ocfs2 fast symlinks are NUL terminated strings stored inline in the
inode data area.  However, disk corruption or a local attacker could, in
theory, remove that NUL.  Because we're using strlen() (my fault,
introduced in a731d1 when removing vfs_follow_link()), we could walk off
the end of that string.

Signed-off-by: Joel Becker <joel.becker@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/ocfs2/symlink.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ocfs2/symlink.c
+++ b/fs/ocfs2/symlink.c
@@ -128,7 +128,7 @@ static void *ocfs2_fast_follow_link(stru
 	}
 
 	/* Fast symlinks can't be large */
-	len = strlen(target);
+	len = strnlen(target, ocfs2_fast_symlink_chars(inode->i_sb));
 	link = kzalloc(len + 1, GFP_NOFS);
 	if (!link) {
 		status = -ENOMEM;


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