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Tue, 28 Jul 2020 17:07:19 +0000 Subject: Re: [PATCH] amdgpu_dm: fix nonblocking atomic commit use-after-free To: Paul Menzel , Mazin Rezk , Duncan <1i5t5.duncan@cox.net> Cc: Kees Cook , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Andrew Morton , =?UTF-8?Q?Christian_K=c3=b6nig?= , Harry Wentland , sunpeng.li@amd.com, Alexander Deucher , mphantomx@yahoo.com.br, regressions@leemhuis.info, anthony.ruhier@gmail.com References: <202007231524.A24720C@keescook> <202007241016.922B094AAA@keescook> <3c92db94-3b62-a70b-8ace-f5e34e8f268f@molgen.mpg.de> <_vGVoFJcOuoIAvGYtkyemUvqEFeZ-AdO4Jk8wsyVv3MwO-6NEVtULxnZzuBJNeHNkCsQ5Kxn5TPQ_VJ6qyj9wXXXX8v-hc3HptnCAu0UYsk=@protonmail.com> <20200724215914.6297cc7e@ws> <0b0fbe35-75cf-ec90-7c3d-bdcedbe217b7@molgen.mpg.de> From: "Kazlauskas, Nicholas" Message-ID: <0edb1498-6c43-27cc-b2fb-71ea5ca1a56c@amd.com> Date: Tue, 28 Jul 2020 13:07:13 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <0b0fbe35-75cf-ec90-7c3d-bdcedbe217b7@molgen.mpg.de> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData: tKObakxShWzy7gnht50gqJVjBiY5OXQz9GeKF+7wocO78vAebgNwFE/A6qHvWNsyJuLu/o/wXuOysgSQAXET2a3TI7btoNOuRIu1/z38CQ16nxtxz0OcVLLPnnCaTeAht6vU2IPtQUtHqxjZ7BwrjmeQ7wjXdy+esoR9YLxNzTp7NeBB15jBjfAOFu4V7/8lTMIGbrqDHgjz+qsWxgTGrPMdVx0FDgil6LHqcwCseVCyipiEqAOtnBY3p5fZ8TMdH8bibjI6mqrabQ3utHVtPawD29KgWGcV2I20HbJzsC9jcGmnAOfdh/kH/UayRotdLfKqojGqPKnWpocL2OeodrsZacmUpjkM8+1fKYnNllbf6v/Zj+f2JxAbloXGQNbfXt9oqmRqzZFwEcu+AyDyJKUYAHKmRLvsKDViOqod+oqxF5fVrlGhjMQC+g/Q12h85wjy0jhKf6DyijcgcG8dFcJ8mZkrJWXRdiqSW748L5YfnHYRo1HeMnoahOAq3p5g X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4bca8ad2-657a-432a-a89a-08d83318af62 X-MS-Exchange-CrossTenant-AuthSource: BYAPR12MB3560.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Jul 2020 17:07:19.4271 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: dDl/DJuFWcE0q5UIkMV6nLtn9S2/msPX4D4JWgrg6RXZ73C83pfNIrYhfW9WD051re8M4uIQKhMLmZb5BEtvKA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4115 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-07-28 5:22 a.m., Paul Menzel wrote: > Dear Linux folks, > > > Am 25.07.20 um 07:20 schrieb Mazin Rezk: >> On Saturday, July 25, 2020 12:59 AM, Duncan wrote: >> >>> On Sat, 25 Jul 2020 03:03:52 +0000 Mazin Rezk wrote: >>> >>>>> Am 24.07.20 um 19:33 schrieb Kees Cook: >>>>> >>>>>> There was a fix to disable the async path for this driver that >>>>>> worked around the bug too, yes? That seems like a safer and more >>>>>> focused change that doesn't revert the SLUB defense for all >>>>>> users, and would actually provide a complete, I think, workaround >>>> >>>> That said, I haven't seen the async disabling patch. If you could >>>> link to it, I'd be glad to test it out and perhaps we can use that >>>> instead. >>> >>> I'm confused. Not to put words in Kees' mouth; /I/ am confused (which >>> admittedly could well be just because I make no claims to be a >>> coder and am simply reading the bug and thread, but I'd appreciate some >>> "unconfusing" anyway). >>> >>> My interpretation of the "async disabling" reference was that it was to >>> comment #30 on the bug: >>> >>> https://bugzilla.kernel.org/show_bug.cgi?id=207383#c30 >>> >>> >>> ... which (if I'm not confused on this point too) appears to be yours. >>> There it was stated... >>> >>> I've also found that this bug exclusively occurs when commit_work is on >>> the workqueue. After forcing drm_atomic_helper_commit to run all of the >>> commits without adding to the workqueue and running the OS, the issue >>> seems to have disappeared. >>> <<<< >>> >>> Would not forcing all commits to run directly, without placing them on >>> the workqueue, be "async disabling"? That's what I /thought/ he was >>> referencing. >> >> Oh, I thought he was referring to a different patch. Kees, could I get >> your confirmation on this? >> >> The change I made actually affected all of the DRM code, although this >> could >> easily be changed to be specific to amdgpu. (By forcing blocking on >> amdgpu_dm's non-blocking commit code) >> >> That said, I'd still need to test further because I only did test it >> for a >> couple of hours then. Although it should work in theory. >> >>> OTOH your base/context swap idea sounds like a possibly "less >>> disturbance" workaround, if it works, and given the point in the >>> commit cycle... (But if it's out Sunday it's likely too late to test >>> and get it in now anyway; if it's another week, tho...) >> >> The base/context swap idea should make the use-after-free behave how it >> did in 5.6. Since the bug doesn't cause an issue in 5.6, it's less of a >> "less disturbance" workaround and more of a "no disturbance" workaround. > > Sorry for bothering, but is there now a solution, besides reverting the > commits, to avoid freezes/crashes *without* performance regressions? > > > Kind regards, > > Paul Mazin's "drm/amd/display: Clear dm_state for fast updates" change accomplishes this, at least as a temporary hack. I've started work on a more large scale fix that we could get in in after. 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dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=amd.com; Received: from BYAPR12MB3560.namprd12.prod.outlook.com (2603:10b6:a03:ae::10) by BY5PR12MB4115.namprd12.prod.outlook.com (2603:10b6:a03:20f::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3216.21; Tue, 28 Jul 2020 17:07:19 +0000 Received: from BYAPR12MB3560.namprd12.prod.outlook.com ([fe80::7d42:c932:e35f:71b1]) by BYAPR12MB3560.namprd12.prod.outlook.com ([fe80::7d42:c932:e35f:71b1%7]) with mapi id 15.20.3216.033; Tue, 28 Jul 2020 17:07:19 +0000 Subject: Re: [PATCH] amdgpu_dm: fix nonblocking atomic commit use-after-free To: Paul Menzel , Mazin Rezk , Duncan <1i5t5.duncan@cox.net> References: <202007231524.A24720C@keescook> <202007241016.922B094AAA@keescook> <3c92db94-3b62-a70b-8ace-f5e34e8f268f@molgen.mpg.de> <_vGVoFJcOuoIAvGYtkyemUvqEFeZ-AdO4Jk8wsyVv3MwO-6NEVtULxnZzuBJNeHNkCsQ5Kxn5TPQ_VJ6qyj9wXXXX8v-hc3HptnCAu0UYsk=@protonmail.com> <20200724215914.6297cc7e@ws> <0b0fbe35-75cf-ec90-7c3d-bdcedbe217b7@molgen.mpg.de> From: "Kazlauskas, Nicholas" Message-ID: <0edb1498-6c43-27cc-b2fb-71ea5ca1a56c@amd.com> Date: Tue, 28 Jul 2020 13:07:13 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; 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charset="us-ascii"; Format="flowed" Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 2020-07-28 5:22 a.m., Paul Menzel wrote: > Dear Linux folks, > > > Am 25.07.20 um 07:20 schrieb Mazin Rezk: >> On Saturday, July 25, 2020 12:59 AM, Duncan wrote: >> >>> On Sat, 25 Jul 2020 03:03:52 +0000 Mazin Rezk wrote: >>> >>>>> Am 24.07.20 um 19:33 schrieb Kees Cook: >>>>> >>>>>> There was a fix to disable the async path for this driver that >>>>>> worked around the bug too, yes? That seems like a safer and more >>>>>> focused change that doesn't revert the SLUB defense for all >>>>>> users, and would actually provide a complete, I think, workaround >>>> >>>> That said, I haven't seen the async disabling patch. If you could >>>> link to it, I'd be glad to test it out and perhaps we can use that >>>> instead. >>> >>> I'm confused. Not to put words in Kees' mouth; /I/ am confused (which >>> admittedly could well be just because I make no claims to be a >>> coder and am simply reading the bug and thread, but I'd appreciate some >>> "unconfusing" anyway). >>> >>> My interpretation of the "async disabling" reference was that it was to >>> comment #30 on the bug: >>> >>> https://bugzilla.kernel.org/show_bug.cgi?id=207383#c30 >>> >>> >>> ... which (if I'm not confused on this point too) appears to be yours. >>> There it was stated... >>> >>> I've also found that this bug exclusively occurs when commit_work is on >>> the workqueue. After forcing drm_atomic_helper_commit to run all of the >>> commits without adding to the workqueue and running the OS, the issue >>> seems to have disappeared. >>> <<<< >>> >>> Would not forcing all commits to run directly, without placing them on >>> the workqueue, be "async disabling"? That's what I /thought/ he was >>> referencing. >> >> Oh, I thought he was referring to a different patch. Kees, could I get >> your confirmation on this? >> >> The change I made actually affected all of the DRM code, although this >> could >> easily be changed to be specific to amdgpu. (By forcing blocking on >> amdgpu_dm's non-blocking commit code) >> >> That said, I'd still need to test further because I only did test it >> for a >> couple of hours then. Although it should work in theory. >> >>> OTOH your base/context swap idea sounds like a possibly "less >>> disturbance" workaround, if it works, and given the point in the >>> commit cycle... (But if it's out Sunday it's likely too late to test >>> and get it in now anyway; if it's another week, tho...) >> >> The base/context swap idea should make the use-after-free behave how it >> did in 5.6. Since the bug doesn't cause an issue in 5.6, it's less of a >> "less disturbance" workaround and more of a "no disturbance" workaround. > > Sorry for bothering, but is there now a solution, besides reverting the > commits, to avoid freezes/crashes *without* performance regressions? > > > Kind regards, > > Paul Mazin's "drm/amd/display: Clear dm_state for fast updates" change accomplishes this, at least as a temporary hack. I've started work on a more large scale fix that we could get in in after. Regards, Nicholas Kazlauskas _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel 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=-6.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 9A44BC433E0 for ; Tue, 28 Jul 2020 17:07:24 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4194A20786 for ; 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charset="us-ascii"; Format="flowed" Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On 2020-07-28 5:22 a.m., Paul Menzel wrote: > Dear Linux folks, > > > Am 25.07.20 um 07:20 schrieb Mazin Rezk: >> On Saturday, July 25, 2020 12:59 AM, Duncan wrote: >> >>> On Sat, 25 Jul 2020 03:03:52 +0000 Mazin Rezk wrote: >>> >>>>> Am 24.07.20 um 19:33 schrieb Kees Cook: >>>>> >>>>>> There was a fix to disable the async path for this driver that >>>>>> worked around the bug too, yes? That seems like a safer and more >>>>>> focused change that doesn't revert the SLUB defense for all >>>>>> users, and would actually provide a complete, I think, workaround >>>> >>>> That said, I haven't seen the async disabling patch. If you could >>>> link to it, I'd be glad to test it out and perhaps we can use that >>>> instead. >>> >>> I'm confused. Not to put words in Kees' mouth; /I/ am confused (which >>> admittedly could well be just because I make no claims to be a >>> coder and am simply reading the bug and thread, but I'd appreciate some >>> "unconfusing" anyway). >>> >>> My interpretation of the "async disabling" reference was that it was to >>> comment #30 on the bug: >>> >>> https://bugzilla.kernel.org/show_bug.cgi?id=207383#c30 >>> >>> >>> ... which (if I'm not confused on this point too) appears to be yours. >>> There it was stated... >>> >>> I've also found that this bug exclusively occurs when commit_work is on >>> the workqueue. After forcing drm_atomic_helper_commit to run all of the >>> commits without adding to the workqueue and running the OS, the issue >>> seems to have disappeared. >>> <<<< >>> >>> Would not forcing all commits to run directly, without placing them on >>> the workqueue, be "async disabling"? That's what I /thought/ he was >>> referencing. >> >> Oh, I thought he was referring to a different patch. Kees, could I get >> your confirmation on this? >> >> The change I made actually affected all of the DRM code, although this >> could >> easily be changed to be specific to amdgpu. (By forcing blocking on >> amdgpu_dm's non-blocking commit code) >> >> That said, I'd still need to test further because I only did test it >> for a >> couple of hours then. Although it should work in theory. >> >>> OTOH your base/context swap idea sounds like a possibly "less >>> disturbance" workaround, if it works, and given the point in the >>> commit cycle... (But if it's out Sunday it's likely too late to test >>> and get it in now anyway; if it's another week, tho...) >> >> The base/context swap idea should make the use-after-free behave how it >> did in 5.6. Since the bug doesn't cause an issue in 5.6, it's less of a >> "less disturbance" workaround and more of a "no disturbance" workaround. > > Sorry for bothering, but is there now a solution, besides reverting the > commits, to avoid freezes/crashes *without* performance regressions? > > > Kind regards, > > Paul Mazin's "drm/amd/display: Clear dm_state for fast updates" change accomplishes this, at least as a temporary hack. I've started work on a more large scale fix that we could get in in after. Regards, Nicholas Kazlauskas _______________________________________________ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx