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Biederman" Cc: Andrew Morton , Andy Lutomirski , Kees Cook , Kusaram Devineni , Peter Zijlstra , Thomas Gleixner , Will Drewry , linux-kernel@vger.kernel.org, Linus Torvalds , Christian Brauner Subject: Re: [PATCH v2 00/14] Short circuit delivery for coredump signals Message-ID: References: <87o6gx9rc4.fsf@email.froward.int.ebiederm.org> <877bnh7tnf.fsf@email.froward.int.ebiederm.org> <877bnb4uyw.fsf_-_@email.froward.int.ebiederm.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On 07/07, Oleg Nesterov wrote: > > Eric, so far I applied the whole series, and I don't see how it can > solve one of the problems I tried to fix in my series. > > Again. A task T has a pending and blocked SIGSYS. si_code = SI_USER. > (although the latter is not strictly necessary) > > force_sig_seccomp(force_coredump => true) sent to T unblocks SIGSYS > and sets SA_IMMUTABLE. > > However, __send_signal_locked() will bypass enqueue_signal() (so it > won't set SIGNAL_GROUP_EXIT) because legacy_queue() is true. > > T calls get_signal(). Now. it can dequeue another synchronous signal. > If that signal has a handler and its sa_mask includes SIGSYS, the task > can return to userspace and survive. > > No? > > Oh... And SIGKILL still can be lost, and I still think this is not good. Hmm. And it seems that V2 doesn't fix the problem I noticed in V1: the dumper thread can be wrong. The first thread which calls get_signal() -> dequeue_exit_signal() will initiate the coredumping, not necessary the faulting thread. This looks very wrong to me. Oleg.