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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id j126sm20471272pfd.113.2021.10.25.14.06.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Oct 2021 14:06:54 -0700 (PDT) Date: Mon, 25 Oct 2021 14:06:54 -0700 From: Kees Cook To: Steven Rostedt Cc: Alexei Starovoitov , Yafang Shao , Andrew Morton , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Petr Mladek , Peter Zijlstra , Alexander Viro , Valentin Schneider , "Zhang, Qiang" , robdclark@chromium.org, Christian Brauner , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Vincent Guittot , "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , dennis.dalessandro@cornelisnetworks.com, mike.marciniszyn@cornelisnetworks.com, Doug Ledford , Jason Gunthorpe , linux-rdma@vger.kernel.org, Network Development , bpf , linux-perf-users@vger.kernel.org, Linux-Fsdevel , linux-mm , LKML , kernel test robot , kbuild test robot Subject: Re: [PATCH v6 00/12] extend task comm from 16 to 24 Message-ID: <202110251406.56F87A3522@keescook> References: <20211025083315.4752-1-laoar.shao@gmail.com> <20211025170503.59830a43@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211025170503.59830a43@gandalf.local.home> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 281EFF000394 X-Stat-Signature: izc9anj9n3n8378131i97poadnh5yja1 Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=PVZq0VU4; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf17.hostedemail.com: domain of keescook@chromium.org designates 209.85.210.177 as permitted sender) smtp.mailfrom=keescook@chromium.org X-HE-Tag: 1635196016-267780 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: On Mon, Oct 25, 2021 at 05:05:03PM -0400, Steven Rostedt wrote: > On Mon, 25 Oct 2021 11:10:09 -0700 > Alexei Starovoitov wrote: > > > It looks like a churn that doesn't really address the problem. > > If we were to allow long names then make it into a pointer and use 16 byte > > as an optimized storage for short names. Any longer name would be a pointer. > > In other words make it similar to dentry->d_iname. > > That would be quite a bigger undertaking too, as it is assumed throughout > the kernel that the task->comm is TASK_COMM_LEN and is nul terminated. And > most locations that save the comm simply use a fixed size string of > TASK_COMM_LEN. Not saying its not feasible, but it would require a lot more > analysis of the impact by changing such a fundamental part of task struct > from a static to something requiring allocation. > > Unless you are suggesting that we truncate like normal the 16 byte names > (to a max of 15 characters), and add a way to hold the entire name for > those locations that understand it. Agreed -- this is a small change for what is already an "uncommon" corner case. I don't think this needs to suddenly become an unbounded string. :) -- Kees Cook