cifs: fix possible memory corruption in CIFSFindNext

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>

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index aac37d99a487bfe9b40d1107ba67973bf212ed54..a80f7bd97b90d541e9305d7e225c708f3f0cd3d1 100644 (file)
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -4079,7 +4079,8 @@ 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");