[v2.6.34-stable 010/165] cifs: fix possible memory corruption in CIFSFindNext

[Paul Gortmaker]

From: Jeff Layton <jlayton@xxxxxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Steve French <sfrench@xxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 fs/cifs/cifssmb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 62e49ab..5171d86 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -3743,7 +3743,8 @@ 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"));
-- 
1.7.12.rc2

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