linux-kernel - [PATCH 42/91] cifs: fix possible memory corruption in CIFSFindNext

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Date:	Sun, 05 Feb 2012 23:10:31 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Jeff Layton <jlayton@...hat.com>,
	Steve French <sfrench@...ibm.com>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: [PATCH 42/91] cifs: fix possible memory corruption in CIFSFindNext

2.6.27-longterm review patch.  If anyone has any objections, please let us know.

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

commit 9438fabb73eb48055b58b89fc51e0bc4db22fabd upstream.

The name_len variable in CIFSFindNext is a signed int that gets set to
the resume_name_len in the cifs_search_info. The resume_name_len however
is unsigned and for some infolevels is populated directly from a 32 bit
value sent by the server.

If the server sends a very large value for this, then that value could
look negative when converted to a signed int. That would make that
value pass the PATH_MAX check later in CIFSFindNext. The name_len would
then be used as a length value for a memcpy. It would then be treated
as unsigned again, and the memcpy scribbles over a ton of memory.

Fix this by making the name_len an unsigned value in CIFSFindNext.

Reported-by: Darren Lavender <dcl@...ine99.gbr.hp.com>
Signed-off-by: Jeff Layton <jlayton@...hat.com>
Signed-off-by: Steve French <sfrench@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 fs/cifs/cifssmb.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

Index: longterm-2.6.27/fs/cifs/cifssmb.c
===================================================================
--- longterm-2.6.27.orig/fs/cifs/cifssmb.c	2012-02-05 22:34:33.755917316 +0100
+++ longterm-2.6.27/fs/cifs/cifssmb.c	2012-02-05 22:34:40.813915010 +0100
@@ -3649,7 +3649,8 @@
 	T2_FNEXT_RSP_PARMS *parms;
 	char *response_data;
 	int rc = 0;
-	int bytes_returned, name_len;
+	int bytes_returned;
+	unsigned int name_len;
 	__u16 params, byte_count;

 	cFYI(1, ("In FindNext"));

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