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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: Re: [PATCH v17] exec: Fix dead-lock in de_thread with ptrace_attach Message-ID: References: <20251105143210.GA25535@redhat.com> <20251111-ankreiden-augen-eadcf9bbdfaa@brauner> 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 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2A0B0C000D X-Stat-Signature: sqc8hgthy6kuabijdkrm64k19eeoraqg X-HE-Tag: 1762866785-285088 X-HE-Meta: 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 Mig5yTKt 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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: On 11/11, Bernd Edlinger wrote: > > On 11/11/25 10:21, Christian Brauner wrote: > > On Wed, Nov 05, 2025 at 03:32:10PM +0100, Oleg Nesterov wrote: > >> > >> This is the most problematic change which I can't review... > >> > >> Firstly, it changes task->mm/real_cred for __ptrace_may_access() and this > >> looks dangerous to me. > > > > Yeah, that is not ok. This is effectively override_creds for real_cred > > and that is not a pattern I want to see us establish at all! Temporary > > credential overrides for the subjective credentials is already terrible > > but at least we have the explicit split between real_cred and cred > > expressely for that. So no, that's not an acceptable solution. > > > > Well when this is absolutely not acceptable then I would have to change > all security engines to be aware of the current and the new credentials. Hmm... even if we find another way to avoid the deadlock? Say, the patches I sent... Oleg.