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Biederman" , Adrian Reber , Thomas Gleixner , Jens Axboe , Alexei Starovoitov , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, tiozhang , Luis Chamberlain , "Paulo Alcantara (SUSE)" , Sergey Senozhatsky , Frederic Weisbecker , YueHaibing , Paul Moore , Aleksa Sarai , Stefan Roesch , Chao Yu , xu xin , Jeff Layton , Jan Kara , David Hildenbrand , Dave Chinner , Shuah Khan , Elena Reshetova , David Windsor , Mateusz Guzik , Ard Biesheuvel , "Joel Fernandes (Google)" , "Matthew Wilcox (Oracle)" , Hans Liljestrand , Penglei Jiang , Lorenzo Stoakes , Adrian Ratiu , Ingo Molnar , "Peter Zijlstra (Intel)" , Cyrill Gorcunov , Eric Dumazet Subject: [RFC PATCH 3/3] ptrace: ensure PTRACE_EVENT_EXIT won't stop if the tracee is killed by exec Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 63D1E18000C X-Stat-Signature: wt5pd9kfyt4h8erdz9yppz3akx4yydwc X-HE-Tag: 1762708615-797772 X-HE-Meta: U2FsdGVkX18ONnuDkyCXfSDTJ7auPucTTVPC+ZABFF0HJaND4ARezx23I0FZ0RNaVNYfgeuOo/NTts3NRkqkekTVtpSj2T/pVHesqNKwBIyry4Z8XkDpvmGaKOGNkl3+x95fuqwc1xtF11ioTPo7Pfmsjdg4vgWsCHg5T6z+UlomNFeM/U20wDUvW0UAJHwujWcjH0TW5j/EBNnNLtUIli+q917bcUvlO329eCX3YcSMtqKvLxRB1N9KR5bGezly0jejItEjirwh2fzQgNQKF2UhA8PIWtR5OyqY81UYiZ3UWwZhog/ATyuBuSu01DeKQ650j7L8kurALTkx1P59nEXZjzsKnzSU2tlMTyn2FE4CX/fk6VfUFRD/XGpjPLIWtcUCkUvcfRpdJ9R3cgLjv55ouUAWGBQogFggmyohSUb25P2h7t/k4s0iShDEGVgWKJaJW7FCSJV+m+729tI4v1i9FbpmNHhcZl6mME2uf/avaqSdP7y8wmGPaEbpOMnDgpWiNpOyl7bd9hw7Pu1cGRaKLQehDyFaVS6fnXLmQjrurWlfZjMPI0veEL6zGb2LBjZGr8liQi8OaZpP2YdKZUbS4Fy60LRNlQBEx15t0fMNrkakpdie6tweKXICbVJsgvuSdvNR4tWBM//BVNgAyrntf9gfhpO4aLMTEcuuJLn/mFuxdoZiiyzY8OlldeTurNxlcfS/a94QCwKi8POGB+Tf7Up5MvHuo0oDYNQwyQikw45ChVv5QMYVIpMplzSm/mJza3o3f3teWqMC1B+FZMXbXViWMxAcpngwovmMNFXB75Z4q5GoAyeHD6FBoOGyACjHxH0A3XF7/8pu57tAwILA3IsrkPdLQ5ME+ldgt15zUYVxEHnjbg0f/pS7iK09DNIIPh1XnaLN6EVACk1ejMqWWx0Z+Rke5R9iPkfU8eqmKhVmVrVQxTIBVkKJ5SyqPPUBNzqfOKZ3ekjExNL 2Rn7gkmY 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 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: List-Subscribe: List-Unsubscribe: The previous patch fixed the deadlock when mt-exec waits for debugger which should reap a zombie thread, but we can hit the same problem if the killed sub-thread stops in ptrace_event(PTRACE_EVENT_EXIT). Change ptrace_stop() to check signal->group_exit_task. This is a user-visible change. But hopefully it can't break anything. Note that the semantics of PTRACE_EVENT_EXIT was never really defined, it depends on /dev/random. Just for example, currently a sub-thread killed by exec will stop, but if it exits on its own and races with exec it will not stop, so nobody can rely on PTRACE_EVENT_EXIT anyway. We really need to finally define what PTRACE_EVENT_EXIT should actually do, but this needs other changes. Signed-off-by: Oleg Nesterov --- kernel/signal.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/signal.c b/kernel/signal.c index 334212044940..59f61e07905b 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2376,6 +2376,10 @@ static int ptrace_stop(int exit_code, int why, unsigned long message, if (!current->ptrace || __fatal_signal_pending(current)) return exit_code; + /* de_thread() -> wait_for_notify_count() waits for us */ + if (current->signal->group_exec_task) + return exit_code; + set_special_state(TASK_TRACED); current->jobctl |= JOBCTL_TRACED; -- 2.25.1.362.g51ebf55