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Biederman" , 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 , 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: <077b63b7-6f5e-aa8e-bf96-a586b481cc46@hotmail.de> Message-ID: Date: Fri, 20 Mar 2020 21:27:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 In-Reply-To: <077b63b7-6f5e-aa8e-bf96-a586b481cc46@hotmail.de> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: ZR0P278CA0019.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:1c::6) To AM6PR03MB5170.eurprd03.prod.outlook.com (2603:10a6:20b:ca::23) X-Microsoft-Original-Message-ID: <60c281a3-5bd0-f01b-60b4-398221fffe5c@hotmail.de> MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.101] (92.77.140.102) by ZR0P278CA0019.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:1c::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2835.18 via Frontend Transport; Fri, 20 Mar 2020 20:27:26 +0000 X-Microsoft-Original-Message-ID: <60c281a3-5bd0-f01b-60b4-398221fffe5c@hotmail.de> X-TMN: [8o2JbL35JfHG0CF/Web1fABngrpEmOdV] X-MS-PublicTrafficType: Email X-IncomingHeaderCount: 49 X-EOPAttributedMessage: 0 X-MS-Office365-Filtering-Correlation-Id: cdc9e6e5-2ba8-4d82-2482-08d7cd0d1bca X-MS-TrafficTypeDiagnostic: DB3EUR04HT111: X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: f+r5n9VUw8/8dIYTVPwzSuxAoiqy0i1lWKx7X4I6i5tR1PYdAnWgmOPcbXUmo1HlMc7oozVdm2GSC7vHKlLMCut0OKM1LFBvKFFfxhGTKXubi1xC1B8CS67Xz2qWlS31C1FjKfmuk9DnjI4vAuMf3ks+I0KKexXy2RI3tPNTUP6C911F/D4CzY6yaYiSUiUx X-MS-Exchange-AntiSpam-MessageData: n+mZZ6uXUYaPFGdRojpj8SG9eSTGW3cNDDoMytoIZ+8yVLRZ86E45SQH2br9uEgTixeRPDQYusUz5p4E+iK81RPW7+EMH+HoJ9unb+JPTBE2Cn2qURpVQIz8OY9+I7BfK0e1fVRmXIg1pbiFniJtGA== X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: cdc9e6e5-2ba8-4d82-2482-08d7cd0d1bca X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Mar 2020 20:27:28.3484 (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: DB3EUR04HT111 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 lock_trace to use the new exec_update_mutex instead of cred_guard_mutex. This fixes possible deadlocks when the trace is accessing /proc/$pid/stack for instance. This should be safe, as the credentials are only used for reading, and task->mm is updated on execve under the new exec_update_mutex. Signed-off-by: Bernd Edlinger --- fs/proc/base.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index c7c6427..fed76abf 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -405,11 +405,11 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns, static int lock_trace(struct task_struct *task) { - int err = mutex_lock_killable(&task->signal->cred_guard_mutex); + int err = mutex_lock_killable(&task->signal->exec_update_mutex); if (err) return err; if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) { - mutex_unlock(&task->signal->cred_guard_mutex); + mutex_unlock(&task->signal->exec_update_mutex); return -EPERM; } return 0; @@ -417,7 +417,7 @@ static int lock_trace(struct task_struct *task) static void unlock_trace(struct task_struct *task) { - mutex_unlock(&task->signal->cred_guard_mutex); + mutex_unlock(&task->signal->exec_update_mutex); } #ifdef CONFIG_STACKTRACE -- 1.9.1