cifs: Fix autonegotiate security settings mismatch

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

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@axis.com>
---
 fs/cifs/smb2pdu.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

merged into cifs-2.6.git for-next and added cc:stable

On Thu, Jan 11, 2018 at 9:00 AM, Daniel N Pettersson
<daniel.n.pettersson@axis.com> wrote:
> From: Daniel N Pettersson <danielnp@axis.com>
>
> 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@axis.com>
> ---
>  fs/cifs/smb2pdu.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index 01346b8..66af1f8 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -733,8 +733,7 @@ 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))
> --
> 2.1.4
>
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