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From: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Newsgroups: gmane.linux.kernel.cifs
Subject: [PATCH] cifs: fix possible memory corruption in CIFSFindNext
Date: Tue, 23 Aug 2011 07:21:28 -0400
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Xref: news.gmane.org gmane.linux.kernel.cifs:4006
Archived-At: <http://permalink.gmane.org/gmane.linux.kernel.cifs/4006>

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.

Cc: <stable-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Reported-by: Darren Lavender <dcl-HN4QTLPn1qTvY7RNz7mR4EEOCMrvLtNR@public.gmane.org>
Signed-off-by: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 fs/cifs/cifssmb.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index f4d0988..950464d 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -4089,7 +4089,8 @@ int CIFSFindNext(const int xid, struct cifs_tcon *tcon,
 	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");
-- 
1.7.6