[SMB3] send channel sequence number in SMB3 requests after reconnects

The ChannelSequence field in the SMB3 header is supposed to be
increased after reconnect to allow the server to distinguish
requests from before and after the reconnect.  We had always
been setting it to zero.  There are cases where incrementing
ChannelSequence on requests after network reconnects can reduce
the chance of data corruptions.

See MS-SMB2 3.2.4.1 and 3.2.7.1

Signed-off-by: Steve French <stfrench@microsoft.com>
Cc: stable@vger.kernel.org # 5.16+

4 files changed, 23 insertions, 1 deletions

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 1588f98660aa..3271be65fd6f 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -747,6 +747,7 @@ struct TCP_Server_Info {
 	 */
 #define CIFS_SERVER_IS_CHAN(server)	(!!(server)->primary_server)
 	struct TCP_Server_Info *primary_server;
+	__u16 channel_sequence_num;  /* incremented on primary channel on each chan reconnect */
 
 #ifdef CONFIG_CIFS_SWN_UPCALL
 	bool use_swn_dstaddr;
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index e19a9c81a5fa..f2d08d0f9373 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -1686,6 +1686,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 		ctx->target_rfc1001_name, RFC1001_NAME_LEN_WITH_NULL);
 	tcp_ses->session_estab = false;
 	tcp_ses->sequence_number = 0;
+	tcp_ses->channel_sequence_num = 0; /* only tracked for primary channel */
 	tcp_ses->reconnect_instance = 1;
 	tcp_ses->lstrp = jiffies;
 	tcp_ses->compress_algorithm = cpu_to_le16(ctx->compression);
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 38bc92371560..25a25193f962 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -172,8 +172,17 @@ smb2_set_credits(struct TCP_Server_Info *server, const int val)
 
 	spin_lock(&server->req_lock);
 	server->credits = val;
-	if (val == 1)
+	if (val == 1) {
 		server->reconnect_instance++;
+		/*
+		 * ChannelSequence updated for all channels in primary channel so that consistent
+		 * across SMB3 requests sent on any channel. See MS-SMB2 3.2.4.1 and 3.2.7.1
+		 */
+		if (CIFS_SERVER_IS_CHAN(server))
+			server->primary_server->channel_sequence_num++;
+		else
+			server->channel_sequence_num++;
+	}
 	scredits = server->credits;
 	in_flight = server->in_flight;
 	spin_unlock(&server->req_lock);
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index a457f07f820d..9c7e46b7e7c7 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -88,9 +88,20 @@ smb2_hdr_assemble(struct smb2_hdr *shdr, __le16 smb2_cmd,
 		  const struct cifs_tcon *tcon,
 		  struct TCP_Server_Info *server)
 {
+	struct smb3_hdr_req *smb3_hdr;
 	shdr->ProtocolId = SMB2_PROTO_NUMBER;
 	shdr->StructureSize = cpu_to_le16(64);
 	shdr->Command = smb2_cmd;
+	if (server->dialect >= SMB30_PROT_ID) {
+		/* After reconnect SMB3 must set ChannelSequence on subsequent reqs */
+		smb3_hdr = (struct smb3_hdr_req *)shdr;
+		/* if primary channel is not set yet, use default channel for chan sequence num */
+		if (CIFS_SERVER_IS_CHAN(server))
+			smb3_hdr->ChannelSequence =
+				cpu_to_le16(server->primary_server->channel_sequence_num);
+		else
+			smb3_hdr->ChannelSequence = cpu_to_le16(server->channel_sequence_num);
+	}
 	if (server) {
 		spin_lock(&server->req_lock);
 		/* Request up to 10 credits but don't go over the limit. */