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Tue, 10 Mar 2020 17:45:14 +0000 From: Bernd Edlinger Subject: [PATCH 1/4] kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve To: "Eric W. Biederman" Cc: Christian Brauner , Kees Cook , Jann Horn , Jonathan Corbet , Alexander Viro , Andrew Morton , Alexey Dobriyan , Thomas Gleixner , Oleg Nesterov , Frederic Weisbecker , Andrei Vagin , Ingo Molnar , "Peter Zijlstra (Intel)" , Yuyang Du , David Hildenbrand , Sebastian Andrzej Siewior , Anshuman Khandual , David Howells , James Morris , Greg Kroah-Hartman , Shakeel Butt , Jason Gunthorpe , Christian Kellner , Andrea Arcangeli , Aleksa Sarai , "Dmitry V. Levin" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "stable@vger.kernel.org" , "linux-api@vger.kernel.org" References: <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> <87zhcq4jdj.fsf_-_@x220.int.ebiederm.org> <878sk94eay.fsf@x220.int.ebiederm.org> <87r1y12yc7.fsf@x220.int.ebiederm.org> <87k13t2xpd.fsf@x220.int.ebiederm.org> <87d09l2x5n.fsf@x220.int.ebiederm.org> <871rq12vxu.fsf@x220.int.ebiederm.org> <877dzt1fnf.fsf@x220.int.ebiederm.org> <875zfcxlwy.fsf@x220.int.ebiederm.org> Message-ID: Date: Tue, 10 Mar 2020 18:45:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 In-Reply-To: <875zfcxlwy.fsf@x220.int.ebiederm.org> Content-Language: en-US X-ClientProxiedBy: ZR0P278CA0020.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:1c::7) To AM6PR03MB5170.eurprd03.prod.outlook.com (2603:10a6:20b:ca::23) X-Microsoft-Original-Message-ID: <030a2087-f995-327b-ac8f-3e2a0fda1c37@hotmail.de> MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.101] (92.77.140.102) by ZR0P278CA0020.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:1c::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2793.15 via Frontend Transport; Tue, 10 Mar 2020 17:45:12 +0000 X-Microsoft-Original-Message-ID: <030a2087-f995-327b-ac8f-3e2a0fda1c37@hotmail.de> X-TMN: [wZuXIGcgdH2Q8W6qKNBoXYGYM/eVthBC] X-MS-PublicTrafficType: Email X-IncomingHeaderCount: 50 X-EOPAttributedMessage: 0 X-MS-Office365-Filtering-Correlation-Id: 99a48d4d-ff98-45a9-c82e-08d7c51ac9a5 X-MS-TrafficTypeDiagnostic: VI1EUR04HT138: X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: PdIIkda5kaGr6lCbIVe8507xJuc7fBfMn0QYZmW8k4t3Q3MbCWDJMMDiWdMmLtl2PFE/YUWOV1FNDYwyRFfzv2vwYeeLLX4U6AlNjdNlzH+bhhOshoQajl8XBjMVIFCeII80crHptCTpj0uLg6yiqXWHj5saLcQQbtl7rsNNXmUiYqStr3jojGpkIk1swnji X-MS-Exchange-AntiSpam-MessageData: HXLp8eDJv28UtDSkPAAw0rFQcA0ga+EyhrywohzN1kVn0SSi/oegskaWg6Gr4IT9WANm82RyL0ANRHysmEbj+7+qV1s92Cl2DdD5/lj9bCJT0x2UzbSqhrIgG6/7OfnS8+SnsUVr7GQJwQY2LY27eg== X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 99a48d4d-ff98-45a9-c82e-08d7c51ac9a5 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Mar 2020 17:45:14.2359 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-CrossTenant-FromEntityHeader: Internet X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1EUR04HT138 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This changes kcmp_epoll_target to use the new exec_update_mutex instead of cred_guard_mutex. This should be safe, as the credentials are only used for reading, and furthermore ->mm and ->sighand are updated on execve, but only under the new exec_update_mutex. Signed-off-by: Bernd Edlinger --- kernel/kcmp.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/kcmp.c b/kernel/kcmp.c index a0e3d7a..b3ff928 100644 --- a/kernel/kcmp.c +++ b/kernel/kcmp.c @@ -173,8 +173,8 @@ static int kcmp_epoll_target(struct task_struct *task1, /* * One should have enough rights to inspect task details. */ - ret = kcmp_lock(&task1->signal->cred_guard_mutex, - &task2->signal->cred_guard_mutex); + ret = kcmp_lock(&task1->signal->exec_update_mutex, + &task2->signal->exec_update_mutex); if (ret) goto err; if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) || @@ -229,8 +229,8 @@ static int kcmp_epoll_target(struct task_struct *task1, } err_unlock: - kcmp_unlock(&task1->signal->cred_guard_mutex, - &task2->signal->cred_guard_mutex); + kcmp_unlock(&task1->signal->exec_update_mutex, + &task2->signal->exec_update_mutex); err: put_task_struct(task1); put_task_struct(task2);