[hardy CVE 1/1] cifs: fix possible memory corruption in CIFSFindNext

[Andy Whitcroft]

From: Jeff Layton <jlayton at redhat.com>

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 at kernel.org>
Reported-by: Darren Lavender <dcl at hppine99.gbr.hp.com>
Signed-off-by: Jeff Layton <jlayton at redhat.com>
Signed-off-by: Steve French <sfrench at us.ibm.com>
Signed-off-by: Suresh Jayaraman <sjayaraman at suse.de>

(backported from commit c32dfffaf59f73bbcf4472141b851a4dc5db2bf0 cifs-2.6.git)
CVE-2011-3191
BugLink: http://bugs.launchpad.net/bugs/834135
Signed-off-by: Andy Whitcroft <apw at canonical.com>
---
 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 a3d2a52..2b99900 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -3651,7 +3651,8 @@ int CIFSFindNext(const int xid, struct cifsTconInfo *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"));
-- 
1.7.4.1