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Biederman" , Kees Cook , Alexander Viro , Christian Brauner , Jan Kara , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH] piped/ptraced coredump (was: Dump smaller VMAs first in ELF cores) Message-ID: <20240804200153.GC27866@redhat.com> References: <20240804152327.GA27866@redhat.com> <20240804185338.GB27866@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Stat-Signature: p1r4qygj3535pf3eckiw87ss8xru48mt X-Rspam-User: X-Rspamd-Queue-Id: 2F068C0008 X-Rspamd-Server: rspam02 X-HE-Tag: 1722801728-413923 X-HE-Meta: U2FsdGVkX196nzY9MuvSE064vwFmrzu6wJaGB8M5fRk6KAFqACYCvkttMQmXgYbL5IRbV+W0YbY0noIZwk0eNLjgM4JNx2RGh147UQ63RqaunB8XckDbGAGcRcQRqVHLnYm3gkpeVQxBP5/RV8bcg93I12kcweQ+FN2cRu/GKlSPP8PR9BR5fpxXArp8oGxpUd5Oym8HHUUdhJTLNh7lRZDuIBa2YeoqsDQy1iHQ1pufreOiWNriGY2U8G73dEmmWLW08jlGZipdyAVfQYCFIxWAAEtlhQmwunON9z7oEGLb+omi94uvgwCgHhjcDngJY+4O+dnKxRplqWwaH047Xm98ZbIcAK2AZfrgM1a//Wu5rc2dNX6CHkLYu9PK741KVqYSA8KaQEDQ3iYNe0uMR17w0mD53o8FbBJpb8AUeiCmy1PFwFQwpnnW5Vq97LC3JXVwMppP5CqIFic57pjtucSsx3Mdz6MpBgkJCYgAN9fdO8Ocso4qUkcNiLfyHEMSKepV4yER7ECsaIFYcNFY2GYtw12UfgPq4d6CIZUnbHRZ6S01q8fQR1qtQRKYa4kbQBmmM0ox+h2mIRHUyduGDijhcN982RO4xRn2slqo2zGhgTK4GAbX/RY1vZSiYW9hOdZ1ApuFRTsZFd8WIrIzr0fgUAXyDMlxXOeJ1y04nUk2BmOZ6psdsyLXUgNtvnGe0G879yJZvf9iTtHWLp++T8h0DnpDYzbt58W2+StmgEj1uNNq/BdRwB5N+vjGZCfELxiyJgAbu+9CBV8Exx5OtLHA0Rl6SyOtBA3kqzAJm7cMV5Ruv/4TPfjncQWHhQRiPX0rde3XDyC16asPGuuPWNK7NauRg2L3eAWoJMtLchtARqL2qnNUqcjyVhyKrcbeq7iLcUDybTfNh1Nvr7g73WDotUNf6a+/nFLBkCXtCJ0Zufw1hD/IW5F4p3qjupMLDj/nrXALf7bp14KxpoJ Frpcn7di oRLWN+S00s6LCpIqCs5QHCqIttcoPXL8ZtbgZcrpomOVPSi5CNuHBZlmJInkEDuGexJ4yYWpD0e7A03eLoG7yxhskg7FXJqeRtXviQC/GN+c5a3GMDQ2Lh+Su0IX4ZWGpoWvS4ThfUPtLZ44Rvc7Ro/hXWBCIAZYlfAnKctKHBdXS/bQmIraDvao5intnCrFd2wudvA/zIqMI7PFfWjneZDoQa2FGovd4/uL0tSbQNP+dew/jUAcVEenvfgOxpUY9fJDrslyQINd5B877Wk9ovoBwuMe2pFBZWm9mzBL+RZA7FaUI+eEQZk31KpVRATJXYL8KeOEc7j6Zi9UxEsgO6aTO/Lirsz0mpxsJ 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 08/04, Linus Torvalds wrote: > > On Sun, 4 Aug 2024 at 11:53, Oleg Nesterov wrote: > > > > Apart from SIGKILL, the dumper already has the full control. > > What do you mean? It's a regular usermodehelper. It gets the dump data > as input. That's all the control it has. I meant, the dumping thread can't exit until the dumper reads the data from stdin or closes the pipe. Until then the damper can read /proc/pid/mem and do other things. > > And note that the dumper can already use ptrace. > > .. with the normal ptrace() rules, yes. > > You realize that some setups literally disable ptrace() system calls, > right? Which your patch now effectively sidesteps. Well. If, say, selinux disables ptrace, then ptrace_attach() in this patch should also fail. But if some setups disable sys_ptrace() as a system call... then yes, I didn't know that. > THAT is why I don't like it. ptrace() is *dangerous*. And horrible ;) > Just adding some implicit tracing willy-nilly needs to be something > people really worry about. Ok, as I said I won't insist. Oleg.