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From:   SeongJae Park <sjpark@amazon.com>
To:     Greg KH <gregkh@linuxfoundation.org>
CC:     SeongJae Park <sjpark@amazon.com>, <sashal@kernel.org>,
        <aams@amazon.com>, <markubo@amazon.com>,
        <linux-kernel@vger.kernel.org>,
        "# 4 . 4 . y" <stable@vger.kernel.org>,
        David Vrabel <david.vrabel@citrix.com>,
        "David S . Miller" <davem@davemloft.net>
Subject: Re: Please apply "xen-netback: delete NAPI instance when queue fails to initialize" to v4.4.y
Date:   Wed, 24 Feb 2021 18:47:32 +0100
Message-ID: <20210224174732.30014-1-sjpark@amazon.com>
In-Reply-To: <YDaLBcj5DJrSWXqU@kroah.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Wed, 24 Feb 2021 18:21:09 +0100 Greg KH <gregkh@linuxfoundation.org> wrote:

> On Wed, Feb 24, 2021 at 06:03:56PM +0100, SeongJae Park wrote:
> > This is a request for merge of upstream commit 4a658527271b ("xen-netback:
> > delete NAPI instance when queue fails to initialize") on v4.4.y tree.
> > 
> > If 'xenvif_connect()' fails after successful 'netif_napi_add()', the napi is
> > not cleaned up.  Because 'create_queues()' frees the queues in its error
> > handling code, if the 'xenvif_free()' is called for the vif, use-after-free
> > occurs. The upstream commit fixes the problem by cleaning up the napi in the
> > 'xenvif_connect()'.
> > 
> > Attaching the original patch below for your convenience.
> 
> The original patch does not apply cleanly.

I tested the commit is cleanly applicable with 'git cherry-pick' before posting
this.  I just tried 'git format-patch ... && git am ...' and confirmed it
doesn't work.  Sorry, my fault.

> 
> > Tested-by: Markus Boehme <markubo@amazon.de>
> 
> What was tested?

We confirmed the unmodified v4.4.y kernel crashes on a stress test that
repeatedly doing netdev attach/detach, while the patch applied version doesn't.

> 
> I backported the patch, but next time, please provide the patch that
> will work properly.

Thanks, and apology for the inconvenience.  I will do the check with posting
patch again rather than only 'git cherry-pick' from next time.


Thanks,
SeongJae Park

> 
> greg k-h