cifs: check if SMB2 PDU size has been padded and suppress the warning

Some SMB2/3 servers, Win2016 but possibly others too, adds padding
not only between PDUs in a compound but also to the final PDU.
This padding extends the PDU to a multiple of 8 bytes.

Check if the unexpected length looks like this might be the case
and avoid triggering the log messages for :

  "SMB2 server sent bad RFC1001 len %d not %d\n"

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index 303d4592ebe7..db0453660ff6 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -238,6 +238,13 @@ smb2_check_message(char *buf, unsigned int len, struct TCP_Server_Info *srvr)
                         return 0;
 
                 /*
+                 * Some windows servers (win2016) will pad also the final
+                 * PDU in a compound to 8 bytes.
+                 */
+                if (((clc_len + 7) & ~7) == len)
+                        return 0;
+
+                /*
                  * MacOS server pads after SMB2.1 write response with 3 bytes
                  * of junk. Other servers match RFC1001 len to actual
                  * SMB2/SMB3 frame length (header + smb2 response specific data)