linux-kernel - [PATCH 3.16 165/410] cifs: Fix autonegotiate security settings mismatch

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Message-ID: <lsq.1528380321.705160280@decadent.org.uk>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Daniel N Pettersson" <danielnp@...s.com>,
        "Steve French" <smfrench@...il.com>
Subject: [PATCH 3.16 165/410] cifs: Fix autonegotiate security settings
 mismatch

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel N Pettersson <danielnp@...s.com>

commit 9aca7e454415f7878b28524e76bebe1170911a88 upstream.

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: Daniel N Pettersson <danielnp@...s.com>
Signed-off-by: Steve French <smfrench@...il.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/cifs/smb2pdu.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -541,8 +541,7 @@ int smb3_validate_negotiate(const unsign
 	}

 	/* 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))