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Fri, 30 Dec 2022 08:45:58 -0500 (EST) Message-ID: Date: Fri, 30 Dec 2022 08:46:25 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [tip:sched/core] [sched] af7f588d8f: WARNING:at_kernel/sched/core.c:#sched_mm_cid_after_execve Content-Language: en-US To: kernel test robot , Peter Zijlstra Cc: oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org References: <202212301353.5c959d72-yujie.liu@intel.com> From: Mathieu Desnoyers In-Reply-To: <202212301353.5c959d72-yujie.liu@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 318641C0016 X-Rspam-User: X-Stat-Signature: 3exbksr6qgf538yc7qxadbmix167jdpx X-HE-Tag: 1672407959-264730 X-HE-Meta: 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 aDA== 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: On 2022-12-30 01:48, kernel test robot wrote: > Greeting, > > FYI, we noticed WARNING:at_kernel/sched/core.c:#sched_mm_cid_after_execve due to commit (built with gcc-11): > [...] > [ 17.747520][ T48] bprm_execve (exec.c:?) > [ 17.748358][ T48] ? call_usermodehelper_exec_work (umh.c:?) > [ 17.749462][ T48] kernel_execve (??:?) > [ 17.750332][ T48] call_usermodehelper_exec_async (umh.c:?) > [ 17.751363][ T48] ? call_usermodehelper_exec_work (umh.c:?) > [ 17.752163][ T48] ret_from_fork (??:?) I suspect this check: void sched_mm_cid_after_execve(struct task_struct *t) { struct mm_struct *mm = t->mm; unsigned long flags; WARN_ON_ONCE((t->flags & PF_KTHREAD) || !t->mm); is too strict. AFAIU the usermodehelper thread is a kernel thread, which happens to have a non-NULL mm after execve. We want to allow usermodehelper threads to use rseq, so I think the appropriate approach here would be to just warn if !t->mm: WARN_ON_ONCE(!t->mm); We should probably apply a similar change to the warning in sched_mm_cid_fork() as well. Thoughts ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com