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[79.242.62.93]) by smtp.gmail.com with ESMTPSA id z7sm4268228wmi.43.2021.09.23.01.08.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Sep 2021 01:08:31 -0700 (PDT) Subject: Re: [PATCH] kernel: introduce prctl(PR_LOG_UACCESS) To: Steven Rostedt Cc: Peter Collingbourne , Catalin Marinas , Will Deacon , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Thomas Gleixner , Andy Lutomirski , Kees Cook , Andrew Morton , Masahiro Yamada , Sami Tolvanen , YiFei Zhu , Colin Ian King , Mark Rutland , Frederic Weisbecker , Viresh Kumar , Andrey Konovalov , Gabriel Krisman Bertazi , Balbir Singh , Chris Hyser , Daniel Vetter , Chris Wilson , Arnd Bergmann , Dmitry Vyukov , Christian Brauner , "Eric W. Biederman" , Alexey Gladkov , Ran Xiaokai , Xiaofeng Cao , Cyrill Gorcunov , Thomas Cedeno , Marco Elver , Alexander Potapenko , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Evgenii Stepanov References: <20210922061809.736124-1-pcc@google.com> <29f1822d-e4cd-eedb-bea8-619db1d56335@redhat.com> <20210922152250.4e7c869a@gandalf.local.home> From: David Hildenbrand Organization: Red Hat Message-ID: <4d70ee3c-ab2a-a0e3-0214-8cc65caf2acd@redhat.com> Date: Thu, 23 Sep 2021 10:08:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210922152250.4e7c869a@gandalf.local.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22.09.21 21:22, Steven Rostedt wrote: > On Wed, 22 Sep 2021 19:46:47 +0200 > David Hildenbrand wrote: > >>> All signals except SIGKILL and SIGSTOP are masked for the interval >>> between the prctl() and the next syscall in order to prevent handlers >>> for intervening asynchronous signals from issuing syscalls that may >>> cause uaccesses from the wrong syscall to be logged. >> >> Stupid question: can this be exploited from user space to effectively >> disable SIGKILL for a long time ... and do we care? > > I first misread it too, but then caught my mistake reading it a second > time. It says "except SIGKILL". So no, it does not disable SIGKILL. Thanks for pointing out the obvious Steve :) -- Thanks, David / dhildenb