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[23.128.96.18]) by mx.google.com with ESMTP id p3si17681793ejy.228.2021.05.17.15.30.32; Mon, 17 May 2021 15:30:55 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@suse.com header.s=susede1 header.b=iR3+DbGv; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=NONE dis=NONE) header.from=suse.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233524AbhEQOPO (ORCPT + 99 others); Mon, 17 May 2021 10:15:14 -0400 Received: from mx2.suse.de ([195.135.220.15]:50952 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236862AbhEQOM1 (ORCPT ); Mon, 17 May 2021 10:12:27 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1621260669; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=S44vK4RdOnJ04XbS2vkRaVaifdqAqJWbTuWTIISy/hw=; b=iR3+DbGvkyg7WQ8Z8cDFgxHoRSgvWIAeS4+DecIQb7fAJrKhgLBfc5ZSxuiHq2XmAhBmQR luVDcXvc2cLSQkLIAonFcQrRB/311xaPJMSYV7yGraVt/7uAQ3jJ8z8lfm7f3GQAxi1t5K 7z9s9bPIyZSS3xPTHT1+bekE/mf2q0Y= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 96EB6B231; Mon, 17 May 2021 14:11:09 +0000 (UTC) Subject: Re: [PATCH 3/8] xen/blkfront: don't take local copy of a request from the ring page To: Jan Beulich Cc: Boris Ostrovsky , Stefano Stabellini , Konrad Rzeszutek Wilk , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Jens Axboe , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org References: <20210513100302.22027-1-jgross@suse.com> <20210513100302.22027-4-jgross@suse.com> <4cbf7b7f-5f00-4aba-4d54-06aa73d1bc32@suse.com> From: Juergen Gross Message-ID: <278182af-044a-9445-bbdb-fdbb65d0da7c@suse.com> Date: Mon, 17 May 2021 16:11:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <4cbf7b7f-5f00-4aba-4d54-06aa73d1bc32@suse.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="r1814kCXy88HKlk6GseNHQ5Jl1bQjvzK4" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --r1814kCXy88HKlk6GseNHQ5Jl1bQjvzK4 Content-Type: multipart/mixed; boundary="3z0SaXV9bT9EMUHkBlogZ1gUM2CrDn6LJ"; protected-headers="v1" From: Juergen Gross To: Jan Beulich Cc: Boris Ostrovsky , Stefano Stabellini , Konrad Rzeszutek Wilk , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Jens Axboe , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Message-ID: <278182af-044a-9445-bbdb-fdbb65d0da7c@suse.com> Subject: Re: [PATCH 3/8] xen/blkfront: don't take local copy of a request from the ring page References: <20210513100302.22027-1-jgross@suse.com> <20210513100302.22027-4-jgross@suse.com> <4cbf7b7f-5f00-4aba-4d54-06aa73d1bc32@suse.com> In-Reply-To: <4cbf7b7f-5f00-4aba-4d54-06aa73d1bc32@suse.com> --3z0SaXV9bT9EMUHkBlogZ1gUM2CrDn6LJ Content-Type: multipart/mixed; boundary="------------D884FEC9E12ABF923568C4A9" Content-Language: en-US This is a multi-part message in MIME format. --------------D884FEC9E12ABF923568C4A9 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable 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 loca= l >> 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 >=20 > Reviewed-by: Jan Beulich > with one remark/question: >=20 >> @@ -703,6 +704,7 @@ static int blkif_queue_rw_req(struct request *req,=20 struct blkfront_ring_info *ri >> { >> struct blkfront_info *info =3D rinfo->dev_info; >> struct blkif_request *ring_req, *extra_ring_req =3D NULL; >> + struct blkif_request *final_ring_req, *final_extra_ring_req; >=20 > Without setting final_extra_ring_req to NULL just like is done for > extra_ring_req, ... >=20 >> @@ -840,10 +845,10 @@ static int blkif_queue_rw_req(struct request *re= q, struct blkfront_ring_info *ri >> if (setup.segments) >> kunmap_atomic(setup.segments); >> =20 >> - /* Keep a private copy so we can reissue requests when recovering. *= / >> - rinfo->shadow[id].req =3D *ring_req; >> + /* Copy request(s) to the ring page. */ >> + *final_ring_req =3D *ring_req; >> if (unlikely(require_extra_req)) >> - rinfo->shadow[extra_id].req =3D *extra_ring_req; >> + *final_extra_ring_req =3D *extra_ring_req; >=20 > ... 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. 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