CIFS: Count SMB3 credits for malformed pending responses

Even if a response is malformed, we should count credits
granted by the server to avoid miscalculations and unnecessary
reconnects due to client or server bugs. If the response has
been received partially, the session will be reconnected anyway
on the next iteration of the demultiplex thread, so counting
credits for such cases shouldn't break things.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsglob.h

@@ -385,8 +385,8 @@ struct smb_version_operations {
 			 struct cifs_fid *);
 	/* calculate a size of SMB message */
 	unsigned int (*calc_smb_size)(void *buf, struct TCP_Server_Info *ptcpi);
-	/* check for STATUS_PENDING and process it in a positive case */
-	bool (*is_status_pending)(char *, struct TCP_Server_Info *, int);
+	/* check for STATUS_PENDING and process the response if yes */
+	bool (*is_status_pending)(char *buf, struct TCP_Server_Info *server);
 	/* check for STATUS_NETWORK_SESSION_EXPIRED */
 	bool (*is_session_expired)(char *);
 	/* send oplock break response */

fs/cifs/cifssmb.c

@@ -1605,7 +1605,7 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	}
 
 	if (server->ops->is_status_pending &&
-	    server->ops->is_status_pending(buf, server, 0)) {
+	    server->ops->is_status_pending(buf, server)) {
 		cifs_discard_remaining_data(server);
 		return -1;
 	}

fs/cifs/connect.c

@@ -1054,7 +1054,7 @@ cifs_handle_standard(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	}
 
 	if (server->ops->is_status_pending &&
-	    server->ops->is_status_pending(buf, server, length))
+	    server->ops->is_status_pending(buf, server))
 		return -1;
 
 	if (!mid)

fs/cifs/smb2ops.c

@@ -1773,14 +1773,14 @@ smb2_close_dir(const unsigned int xid, struct cifs_tcon *tcon,
 * the number of credits and return true. Otherwise - return false.
 */
 static bool
-smb2_is_status_pending(char *buf, struct TCP_Server_Info *server, int length)
+smb2_is_status_pending(char *buf, struct TCP_Server_Info *server)
 {
 	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buf;
 
 	if (shdr->Status != STATUS_PENDING)
 		return false;
 
-	if (!length) {
+	if (shdr->CreditRequest) {
 		spin_lock(&server->req_lock);
 		server->credits += le16_to_cpu(shdr->CreditRequest);
 		spin_unlock(&server->req_lock);
@@ -3239,7 +3239,7 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 	}
 
 	if (server->ops->is_status_pending &&
-			server->ops->is_status_pending(buf, server, 0))
+			server->ops->is_status_pending(buf, server))
 		return -1;
 
 	/* set up first two iov to get credits */