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Biederman" Cc: Jann Horn , Christian Brauner , 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" , Arnd Bergmann , Sargun Dhillon References: <877dztz415.fsf@x220.int.ebiederm.org> <20200309201729.yk5sd26v4bz4gtou@wittgenstein> <87k13txnig.fsf@x220.int.ebiederm.org> <20200310085540.pztaty2mj62xt2nm@wittgenstein> <87wo7svy96.fsf_-_@x220.int.ebiederm.org> <87k13sui1p.fsf@x220.int.ebiederm.org> <87lfo8rkqo.fsf@x220.int.ebiederm.org> <202003111148.19578AA@keescook> Message-ID: Date: Sat, 14 Mar 2020 10:12:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 In-Reply-To: <202003111148.19578AA@keescook> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: ZRAP278CA0011.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:10::21) To AM6PR03MB5170.eurprd03.prod.outlook.com (2603:10a6:20b:ca::23) X-Microsoft-Original-Message-ID: <23b22eca-8f06-6036-c51c-6a87f559c2f6@hotmail.de> MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.101] (92.77.140.102) by ZRAP278CA0011.CHEP278.PROD.OUTLOOK.COM (2603:10a6:910:10::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2814.16 via Frontend Transport; Sat, 14 Mar 2020 09:12:12 +0000 X-Microsoft-Original-Message-ID: <23b22eca-8f06-6036-c51c-6a87f559c2f6@hotmail.de> X-TMN: [TOOIoRbPJhaUmm2QCnSS9uc4EfUfaL77] X-MS-PublicTrafficType: Email X-IncomingHeaderCount: 50 X-EOPAttributedMessage: 0 X-MS-Office365-Filtering-Correlation-Id: a164edd3-e313-422a-b43f-08d7c7f7c8f6 X-MS-TrafficTypeDiagnostic: HE1EUR01HT032: X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: znmYawuvz+lGrWm1cAxK0euN4MrulX7G+PBhM1sc4edD5nzygIAKiwLMSzOnY7xsThbpCks1WljtEa5ZWBweKKL0XGp+bHawdpEBboevWTU8fpcUS8FStquC7+4SWJqyRkqiO+0oGBVXcm60KDThihFebKaL0n+VwITjQeQN5naqeDUW4M1pWgtmRnqsJmj9 X-MS-Exchange-AntiSpam-MessageData: y+wj5sYdckEoDefowsMI3A9TmwPKNEM7n8/Hf4DKDIMVJ8cJSvf+RZgVU4VB/9wB5Vl+1yIW+wgrGsdwV0TJiP2YZVCtf2ghS55wN32nc7BLPdlvNs5SaHDcRXxNKk+Q3i7Zbey9yDoqcYY10YSgnw== X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: a164edd3-e313-422a-b43f-08d7c7f7c8f6 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Mar 2020 09:12:14.1943 (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: HE1EUR01HT032 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 __pidfd_fget to use the new exec_update_mutex instead of cred_guard_mutex. This should be safe, as the credentials do not change before exec_update_mutex is locked. Therefore whatever file access is possible with holding the cred_guard_mutex here is also possbile with the exec_update_mutex. Signed-off-by: Bernd Edlinger --- kernel/pid.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) This replaces Eric's "[PATCH] pidfd: Stop taking cred_guard_mutex" diff --git a/kernel/pid.c b/kernel/pid.c index 0f4ecb5..04821f4 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -584,7 +584,7 @@ static struct file *__pidfd_fget(struct task_struct *task, int fd) struct file *file; int ret; - ret = mutex_lock_killable(&task->signal->cred_guard_mutex); + ret = mutex_lock_killable(&task->signal->exec_update_mutex); if (ret) return ERR_PTR(ret); @@ -593,7 +593,7 @@ static struct file *__pidfd_fget(struct task_struct *task, int fd) else file = ERR_PTR(-EPERM); - mutex_unlock(&task->signal->cred_guard_mutex); + mutex_unlock(&task->signal->exec_update_mutex); return file ?: ERR_PTR(-EBADF); } -- 1.9.1