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[209.85.208.172]) by smtp.gmail.com with ESMTPSA id k22sm235542ljj.85.2020.04.28.13.35.58 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Apr 2020 13:35:58 -0700 (PDT) Received: by mail-lj1-f172.google.com with SMTP id e25so163867ljg.5 for ; Tue, 28 Apr 2020 13:35:58 -0700 (PDT) X-Received: by 2002:a2e:9a54:: with SMTP id k20mr17484898ljj.265.1588106157681; Tue, 28 Apr 2020 13:35:57 -0700 (PDT) MIME-Version: 1.0 References: <87imi8nzlw.fsf@x220.int.ebiederm.org> <20200411182043.GA3136@redhat.com> <20200412195049.GA23824@redhat.com> <20200428190836.GC29960@redhat.com> In-Reply-To: <20200428190836.GC29960@redhat.com> From: Linus Torvalds Date: Tue, 28 Apr 2020 13:35:41 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1 To: Oleg Nesterov Cc: Jann Horn , Bernd Edlinger , "Eric W. Biederman" , Waiman Long , Ingo Molnar , Will Deacon , Linux Kernel Mailing List , Alexey Gladkov Content-Type: multipart/mixed; boundary="0000000000006586b205a45fc75c" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --0000000000006586b205a45fc75c Content-Type: text/plain; charset="UTF-8" On Tue, Apr 28, 2020 at 12:08 PM Oleg Nesterov wrote: > > Oops. I can update that old patch but somehow I thought there is a better > plan which I don't yet understand... I don't think any plan survived reality. Unless we want to do something *really* hacky.. The attached patch is not meant to be serious. > And, IIRC, Jan had some ideas how to rework the new creds calculation in > execve paths to avoid the cred_guard_mutex deadlock? I'm not sure how you'd do that. Execve() fundamentally needs to serialize with PTRACE_ATTACH somehow, since the whole point is that "tsk->ptrace" changes how the credentials are interpreted. So PTRACE_ATTACH doesn't really _change_ the credentials, but it very much changes what execve() will do with them. But I guess we could do a "if somebody attached to us while we did the execve(), just repeat the whole thing" Jann, what was your clever idea? Maybe it got lost in the long thread.. 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