linux-kernel - Re: [PATCH v2 1/3] xen: xenbus_dev_frontend: Fix XS_TRANSACTION

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Message-ID: <a0a062fa-3245-359a-2d1b-0542a1b274d8@oracle.com>
Date:   Wed, 21 Mar 2018 17:13:21 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Simon Gaiser <simon@...isiblethingslab.com>,
        xen-devel@...ts.xenproject.org
Cc:     stable@...r.kernel.org, Juergen Gross <jgross@...e.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] xen: xenbus_dev_frontend: Fix XS_TRANSACTION_END
 handling

On 03/14/2018 10:43 PM, Simon Gaiser wrote:
> Commit fd8aa9095a95 ("xen: optimize xenbus driver for multiple
> concurrent xenstore accesses") made a subtle change to the semantic of
> xenbus_dev_request_and_reply() and xenbus_transaction_end().
>
> Before on an error response to XS_TRANSACTION_END
> xenbus_dev_request_and_reply() would not decrement the active
> transaction counter. But xenbus_transaction_end() has always counted the
> transaction as finished regardless of the response.
>
> The new behavior is that xenbus_dev_request_and_reply() and
> xenbus_transaction_end() will always count the transaction as finished
> regardless the response code (handled in xs_request_exit()).
>
> But xenbus_dev_frontend tries to end a transaction on closing of the
> device if the XS_TRANSACTION_END failed before. Trying to close the
> transaction twice corrupts the reference count. So fix this by also
> considering a transaction closed if we have sent XS_TRANSACTION_END once
> regardless of the return code.
>
> Cc: <stable@...r.kernel.org> # 4.11
> Fixes: fd8aa9095a95 ("xen: optimize xenbus driver for multiple concurrent xenstore accesses")
> Signed-off-by: Simon Gaiser <simon@...isiblethingslab.com>

Applied the series to for-linus-4.17

-boris