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[23.128.96.18]) by mx.google.com with ESMTP id t11si6498179jal.23.2021.07.09.06.59.59; Fri, 09 Jul 2021 07:00:12 -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=c2FLhMJ8; 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 S231942AbhGIOBX (ORCPT + 99 others); Fri, 9 Jul 2021 10:01:23 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:35720 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231756AbhGIOBW (ORCPT ); Fri, 9 Jul 2021 10:01:22 -0400 Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 742A722180; Fri, 9 Jul 2021 13:58:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1625839118; 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=TP1/uoVP2wkmjJxosE1T60JaJRCCcXfD2nkG/A4nXMI=; b=c2FLhMJ8+yG3MTvCaSzH5E4acsH8MFSWwJ3O1uxntsY5+2FefFEGzc2l9qc1l305EysCBv 0XzaKsaaGYVuYXjWWYCbkXYO0gyM5wdc3eoAl783b0AZhdfY9hmQRG6mgiCgz1+Y/LjuoE JF/qPVWOwYEk+aXuDVLSWumr7vw6BTI= Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap1.suse-dmz.suse.de (Postfix) with ESMTPS id 3D7DD137F8; Fri, 9 Jul 2021 13:58:38 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id l3W+DQ5W6GCYeQAAGKfGzw (envelope-from ); Fri, 09 Jul 2021 13:58:38 +0000 Subject: Re: [PATCH v2 3/3] xen/blkfront: don't trust the backend response data blindly To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Boris Ostrovsky , Stefano Stabellini , Konrad Rzeszutek Wilk , Jens Axboe References: <20210708124345.10173-1-jgross@suse.com> <20210708124345.10173-4-jgross@suse.com> From: Juergen Gross Message-ID: <4f460d31-c4da-8a58-8ee5-7735f5260f08@suse.com> Date: Fri, 9 Jul 2021 15:58:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="PtD6XltbThet5UCMvmi5pahWMOzO45Xvp" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --PtD6XltbThet5UCMvmi5pahWMOzO45Xvp Content-Type: multipart/mixed; boundary="S35JlfSQdS3KAz9fiFZDLgLQ5ZAlpJMxS"; protected-headers="v1" From: Juergen Gross To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Boris Ostrovsky , Stefano Stabellini , Konrad Rzeszutek Wilk , Jens Axboe Message-ID: <4f460d31-c4da-8a58-8ee5-7735f5260f08@suse.com> Subject: Re: [PATCH v2 3/3] xen/blkfront: don't trust the backend response data blindly References: <20210708124345.10173-1-jgross@suse.com> <20210708124345.10173-4-jgross@suse.com> In-Reply-To: --S35JlfSQdS3KAz9fiFZDLgLQ5ZAlpJMxS Content-Type: multipart/mixed; boundary="------------15EFA2D45E58C234A1B0B486" Content-Language: en-US This is a multi-part message in MIME format. --------------15EFA2D45E58C234A1B0B486 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 09.07.21 11:42, Roger Pau Monn=C3=A9 wrote: > On Thu, Jul 08, 2021 at 02:43:45PM +0200, Juergen Gross wrote: >> Today blkfront will trust the backend to send only sane response data.= >> In order to avoid privilege escalations or crashes in case of maliciou= s >> backends verify the data to be within expected limits. Especially make= >> sure that the response always references an outstanding request. >> >> Introduce a new state of the ring BLKIF_STATE_ERROR which will be >> switched to in case an inconsistency is being detected. Recovering fro= m >> this state is possible only via removing and adding the virtual device= >> again (e.g. via a suspend/resume cycle). >> >> Signed-off-by: Juergen Gross >=20 > Acked-by: Roger Pau Monn=C3=A9 >> @@ -1555,11 +1561,17 @@ static irqreturn_t blkif_interrupt(int irq, vo= id *dev_id) >> =20 >> spin_lock_irqsave(&rinfo->ring_lock, flags); >> again: >> - rp =3D rinfo->ring.sring->rsp_prod; >> - rmb(); /* Ensure we see queued responses up to 'rp'. */ >> + rp =3D READ_ONCE(rinfo->ring.sring->rsp_prod); >> + virt_rmb(); /* Ensure we see queued responses up to 'rp'. */ >=20 > Is the READ_ONCE strictly needed? Doesn't the barrier prevent rp from > not being loaded at this point? I asked Jan the same and he didn't want to rule that out. Additionally the READ_ONCE() helps against (rather improbable) load tearing of the compiler. >> + op =3D rinfo->shadow[id].req.operation; >> + if (op =3D=3D BLKIF_OP_INDIRECT) >> + op =3D rinfo->shadow[id].req.u.indirect.indirect_op; >> + if (bret.operation !=3D op) { >> + pr_alert("%s: response has wrong operation (%u instead of %u)\n", >> + info->gd->disk_name, bret.operation, op); >=20 > You could also use op_name here, but I guess this could mask the > operation as 'unknown' for any number out of the defined ones. This case shouldn't happen normally, so having the numerical value is enough and will help for hiding any undefined op. >> @@ -1635,8 +1662,8 @@ static irqreturn_t blkif_interrupt(int irq, void= *dev_id) >> case BLKIF_OP_READ: >> case BLKIF_OP_WRITE: >> if (unlikely(bret.status !=3D BLKIF_RSP_OKAY)) >> - dev_dbg(&info->xbdev->dev, "Bad return from blkdev data " >> - "request: %x\n", bret.status); >> + dev_dbg_ratelimited(&info->xbdev->dev, >> + "Bad return from blkdev data request: %x\n", bret.status); >=20 > Since you are touching the line, could you use %#x here? It's IMO not > obvious from the context this status will be printed in hex base. Also > bret.status parameter could be split into a newline. Fine with me. 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