cifs: Fix autonegotiate security settings mismatch

Autonegotiation gives a security settings mismatch error if the SMB
server selects an SMBv3 dialect that isn't SMB3.02. The exact error is
"protocol revalidation - security settings mismatch".
This can be tested using Samba v4.2 or by setting the global Samba
setting max protocol = SMB3_00.

The check that fails in smb3_validate_negotiate is the dialect
verification of the negotiate info response. This is because it tries
to verify against the protocol_id in the global smbdefault_values. The
protocol_id in smbdefault_values is SMB3.02.
In SMB2_negotiate the protocol_id in smbdefault_values isn't updated,
it is global so it probably shouldn't be, but server->dialect is.

This patch changes the check in smb3_validate_negotiate to use
server->dialect instead of server->vals->protocol_id. The patch works
with autonegotiate and when using a specific version in the vers mount
option.
Signed-off-by: NDaniel N Pettersson <danielnp@axis.com>
Signed-off-by: NSteve French <smfrench@gmail.com>
CC: Stable <stable@vger.kernel.org>

fs/cifs/smb2pdu.c

@@ -700,8 +700,7 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
 	}
 
 	/* check validate negotiate info response matches what we got earlier */
-	if (pneg_rsp->Dialect !=
-			cpu_to_le16(tcon->ses->server->vals->protocol_id))
+	if (pneg_rsp->Dialect != cpu_to_le16(tcon->ses->server->dialect))
 		goto vneg_out;
 
 	if (pneg_rsp->SecurityMode != cpu_to_le16(tcon->ses->server->sec_mode))