From: Juergen Gross <jgross@suse.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"Roger Pau Monné" <roger.pau@citrix.com>,
"Jens Axboe" <axboe@kernel.dk>,
xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
linux-block@vger.kernel.org
Subject: Re: [PATCH 3/8] xen/blkfront: don't take local copy of a request from the ring page
Date: Mon, 17 May 2021 16:11:08 +0200 [thread overview]
Message-ID: <278182af-044a-9445-bbdb-fdbb65d0da7c@suse.com> (raw)
In-Reply-To: <4cbf7b7f-5f00-4aba-4d54-06aa73d1bc32@suse.com>
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On 17.05.21 16:01, Jan Beulich wrote:
> On 13.05.2021 12:02, Juergen Gross wrote:
>> In order to avoid a malicious backend being able to influence the local
>> copy of a request build the request locally first and then copy it to
>> the ring page instead of doing it the other way round as today.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> with one remark/question:
>
>> @@ -703,6 +704,7 @@ static int blkif_queue_rw_req(struct request *req,
struct blkfront_ring_info *ri
>> {
>> struct blkfront_info *info = rinfo->dev_info;
>> struct blkif_request *ring_req, *extra_ring_req = NULL;
>> + struct blkif_request *final_ring_req, *final_extra_ring_req;
>
> Without setting final_extra_ring_req to NULL just like is done for
> extra_ring_req, ...
>
>> @@ -840,10 +845,10 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
>> if (setup.segments)
>> kunmap_atomic(setup.segments);
>>
>> - /* Keep a private copy so we can reissue requests when recovering. */
>> - rinfo->shadow[id].req = *ring_req;
>> + /* Copy request(s) to the ring page. */
>> + *final_ring_req = *ring_req;
>> if (unlikely(require_extra_req))
>> - rinfo->shadow[extra_id].req = *extra_ring_req;
>> + *final_extra_ring_req = *extra_ring_req;
>
> ... are you sure all supported compilers will recognize the
> conditional use and not warn about use of a possibly uninitialized
> variable?
Hmm, probably better safe than sorry. Will change it.
Juergen
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next prev parent reply other threads:[~2021-05-17 14:13 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 10:02 [PATCH 0/8] xen: harden frontends against malicious backends Juergen Gross
2021-05-13 10:02 ` [PATCH 2/8] xen/blkfront: read response from backend only once Juergen Gross
2021-05-17 13:50 ` Jan Beulich
2021-05-13 10:02 ` [PATCH 3/8] xen/blkfront: don't take local copy of a request from the ring page Juergen Gross
2021-05-17 14:01 ` Jan Beulich
2021-05-17 14:11 ` Juergen Gross [this message]
2021-05-13 10:02 ` [PATCH 4/8] xen/blkfront: don't trust the backend response data blindly Juergen Gross
2021-05-17 14:11 ` Jan Beulich
2021-05-17 14:23 ` Juergen Gross
2021-05-17 15:12 ` Jan Beulich
2021-05-17 15:22 ` Juergen Gross
2021-05-17 15:33 ` Jan Beulich
2021-07-08 5:47 ` Juergen Gross
2021-07-08 6:37 ` Jan Beulich
2021-07-08 6:40 ` Juergen Gross
2021-07-08 6:52 ` Jan Beulich
2021-07-08 6:56 ` Juergen Gross
2021-05-21 10:43 ` [PATCH 0/8] xen: harden frontends against malicious backends Marek Marczykowski-Górecki
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