linux-kernel - Re: [PATCH 4.4 06/28] cifs: Do not send echoes before Negotiate is complete

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Date:   Tue, 09 May 2017 13:13:03 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Sachin Prabhu <sprabhu@...hat.com>,
        Pavel Shilovsky <pshilov@...rosoft.com>,
        Steve French <smfrench@...il.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jonathan Liu <net147@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 4.4 06/28] cifs: Do not send echoes before Negotiate is
 complete

On Tue, 2017-04-25 at 16:08 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Sachin Prabhu <sprabhu@...hat.com>
> 
> commit 62a6cfddcc0a5313e7da3e8311ba16226fe0ac10 upstream.
> 
> commit 4fcd1813e640 ("Fix reconnect to not defer smb3 session reconnect
> long after socket reconnect") added support for Negotiate requests to
> be initiated by echo calls.
> 
> To avoid delays in calling echo after a reconnect, I added the patch
> introduced by the commit b8c600120fc8 ("Call echo service immediately
> after socket reconnect").

The second commit hasn't actually been applied to any stable branches
(so this one didn't need to be).  Should it be?

Ben.

> This has however caused a regression with cifs shares which do not have
> support for echo calls to trigger Negotiate requests. On connections
> which need to call Negotiation, the echo calls trigger an error which
> triggers a reconnect which in turn triggers another echo call. This
> results in a loop which is only broken when an operation is performed on
> the cifs share. For an idle share, it can DOS a server.
[...]

-- 
Ben Hutchings
Software Developer, Codethink Ltd.