ksmbd: validate smb request protocol id

This patch add the validation for smb request protocol id.
If it is not one of the four ids(SMB1_PROTO_NUMBER, SMB2_PROTO_NUMBER,
SMB2_TRANSFORM_PROTO_NUM, SMB2_COMPRESSION_TRANSFORM_ID), don't allow
processing the request. And this will fix the following KASAN warning
also.

[   13.905265] BUG: KASAN: slab-out-of-bounds in init_smb2_rsp_hdr+0x1b9/0x1f0
[   13.905900] Read of size 16 at addr ffff888005fd2f34 by task kworker/0:2/44
...
[   13.908553] Call Trace:
[   13.908793]  <TASK>
[   13.908995]  dump_stack_lvl+0x33/0x50
[   13.909369]  print_report+0xcc/0x620
[   13.910870]  kasan_report+0xae/0xe0
[   13.911519]  kasan_check_range+0x35/0x1b0
[   13.911796]  init_smb2_rsp_hdr+0x1b9/0x1f0
[   13.912492]  handle_ksmbd_work+0xe5/0x820

Reported-by: Chih-Yen Chang <[email protected]>
Signed-off-by: Namjae Jeon <[email protected]>

Author: namjaejeon

connection.c

@@ -382,8 +382,6 @@ int ksmbd_conn_handler_loop(void *p)
 			break;
 
 		memcpy(conn->request_buf, hdr_buf, sizeof(hdr_buf));
-		if (!ksmbd_smb_request(conn))
-			break;
 
 		/*
 		 * We already read 4 bytes to find out PDU size, now
@@ -401,6 +399,9 @@ int ksmbd_conn_handler_loop(void *p)
 			continue;
 		}
 
+		if (!ksmbd_smb_request(conn))
+			break;
+
 		if (((struct smb2_hdr *)smb2_get_msg(conn->request_buf))->ProtocolId ==
 		    SMB2_PROTO_NUMBER) {
 			if (pdu_size < SMB2_MIN_SUPPORTED_HEADER_SIZE)

smb2pdu.h

@@ -109,6 +109,7 @@
 
 #define SMB2_PROTO_NUMBER cpu_to_le32(0x424d53fe) /* 'B''M''S' */
 #define SMB2_TRANSFORM_PROTO_NUM cpu_to_le32(0x424d53fd)
+#define SMB2_COMPRESSION_TRANSFORM_ID cpu_to_le32(0x424d53fc)
 
 #define SMB21_DEFAULT_IOSIZE	(1024 * 1024)
 #define SMB3_DEFAULT_IOSIZE	(4 * 1024 * 1024)

smb_common.c

@@ -194,7 +194,19 @@ int ksmbd_verify_smb_message(struct ksmbd_work *work)
  */
 bool ksmbd_smb_request(struct ksmbd_conn *conn)
 {
-	return conn->request_buf[0] == 0;
+	__le32 *proto = (__le32 *)smb2_get_msg(conn->request_buf);
+
+	if (*proto == SMB2_COMPRESSION_TRANSFORM_ID) {
+		pr_err_ratelimited("smb2 compression not support yet");
+		return false;
+	}
+
+	if (*proto != SMB1_PROTO_NUMBER &&
+	    *proto != SMB2_PROTO_NUMBER &&
+	    *proto != SMB2_TRANSFORM_PROTO_NUM)
+		return false;
+
+	return true;
 }
 
 static bool supported_protocol(int idx)