cifs: fix possible memory corruption in CIFSFindNext, CVE-2011-3191

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

(cherry-picked from commit c32dfffaf59f73bbcf4472141b851a4dc5db2bf0 cifs-2.6.git)
CVE-2011-3191
BugLink: http://bugs.launchpad.net/bugs/834135
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 904aa47..e9abcf9 100644 (file)
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -3805,7 +3805,8 @@ 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");