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Thu, 21 May 2020 14:46:04 -0400 (EDT) Date: Thu, 21 May 2020 20:46:02 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Boris Ostrovsky Subject: Re: [PATCH] xen/events: avoid NULL pointer dereference in evtchn_from_irq() Message-ID: <20200521184602.GP98582@mail-itl> References: <20200319071428.12115-1-jgross@suse.com> <30719c35-6de7-d400-7bb8-cff4570f8971@oracle.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KR/qxknboQ7+Tpez" Content-Disposition: inline In-Reply-To: <30719c35-6de7-d400-7bb8-cff4570f8971@oracle.com> X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , xen-devel@lists.xenproject.org, Stefano Stabellini , linux-kernel@vger.kernel.org, stable@vger.kernel.org Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" --KR/qxknboQ7+Tpez Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH] xen/events: avoid NULL pointer dereference in evtchn_from_irq() On Thu, May 21, 2020 at 01:22:03PM -0400, Boris Ostrovsky wrote: > On 3/19/20 3:14 AM, Juergen Gross wrote: > > There have been reports of races in evtchn_from_irq() where the info > > pointer has been NULL. > > > > Avoid that case by testing info before dereferencing it. > > > > In order to avoid accessing a just freed info structure do the kfree() > > via kfree_rcu(). >=20 >=20 > Looks like noone ever responded to this. >=20 >=20 > This change looks fine but is there a background on the problem? I > looked in the archives and didn't find the relevant discussion. Here is the original bug report: https://xen.markmail.org/thread/44apwkwzeme4uavo --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? --KR/qxknboQ7+Tpez Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAl7GzGkACgkQ24/THMrX 1yygDAf/RzUmiuF2TM7HvZsoGQmZxnc+ZrcCx9F+FXoYyHUYYjyoj5hnMWPJit1g GPLie+6PbPhjOyC+6tYK9TGgEv2HxyO8PNLTWDRDRnxrf8rBTqMKRvcbm8FYZV+J 9baXNldjf6TvgddPwik9bqetHX+e/QpyeovpcSOzbP1dXKWnxUbypEinsiNxtT97 vkiW/LfYtzb8arPdFVmVl/9YPmvk+080mm2eTQYARy7qVlM70zqsvtWBYQYFcxd2 N7OH7AoSARVyncbIT1B5bTrte9HTFB4ewJ1CvTvc3wOGDbUCiyVz7nDxNRQo6/S/ 3x7RfR3nRBE3RwMeEj2cAdsgzOkI9g== =oact -----END PGP SIGNATURE----- --KR/qxknboQ7+Tpez-- From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AB24C433E0 for ; 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Thu, 21 May 2020 14:46:04 -0400 (EDT) Date: Thu, 21 May 2020 20:46:02 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Boris Ostrovsky Cc: Juergen Gross , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Stefano Stabellini , stable@vger.kernel.org Subject: Re: [PATCH] xen/events: avoid NULL pointer dereference in evtchn_from_irq() Message-ID: <20200521184602.GP98582@mail-itl> References: <20200319071428.12115-1-jgross@suse.com> <30719c35-6de7-d400-7bb8-cff4570f8971@oracle.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="KR/qxknboQ7+Tpez" Content-Disposition: inline In-Reply-To: <30719c35-6de7-d400-7bb8-cff4570f8971@oracle.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --KR/qxknboQ7+Tpez Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH] xen/events: avoid NULL pointer dereference in evtchn_from_irq() On Thu, May 21, 2020 at 01:22:03PM -0400, Boris Ostrovsky wrote: > On 3/19/20 3:14 AM, Juergen Gross wrote: > > There have been reports of races in evtchn_from_irq() where the info > > pointer has been NULL. > > > > Avoid that case by testing info before dereferencing it. > > > > In order to avoid accessing a just freed info structure do the kfree() > > via kfree_rcu(). >=20 >=20 > Looks like noone ever responded to this. >=20 >=20 > This change looks fine but is there a background on the problem? I > looked in the archives and didn't find the relevant discussion. Here is the original bug report: https://xen.markmail.org/thread/44apwkwzeme4uavo --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? --KR/qxknboQ7+Tpez Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAl7GzGkACgkQ24/THMrX 1yygDAf/RzUmiuF2TM7HvZsoGQmZxnc+ZrcCx9F+FXoYyHUYYjyoj5hnMWPJit1g GPLie+6PbPhjOyC+6tYK9TGgEv2HxyO8PNLTWDRDRnxrf8rBTqMKRvcbm8FYZV+J 9baXNldjf6TvgddPwik9bqetHX+e/QpyeovpcSOzbP1dXKWnxUbypEinsiNxtT97 vkiW/LfYtzb8arPdFVmVl/9YPmvk+080mm2eTQYARy7qVlM70zqsvtWBYQYFcxd2 N7OH7AoSARVyncbIT1B5bTrte9HTFB4ewJ1CvTvc3wOGDbUCiyVz7nDxNRQo6/S/ 3x7RfR3nRBE3RwMeEj2cAdsgzOkI9g== =oact -----END PGP SIGNATURE----- --KR/qxknboQ7+Tpez--