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[209.85.208.51]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5b839c24084sm5308407a12.30.2024.08.05.14.28.39 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Aug 2024 14:28:39 -0700 (PDT) Received: by mail-ed1-f51.google.com with SMTP id 4fb4d7f45d1cf-5ba43b433beso2515360a12.1 for ; Mon, 05 Aug 2024 14:28:39 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCVcV8HsHr+UMn2vWN4qVkEDNprtoIm30drCqnCUjy1sSAov9R5bh971gxx8Unl6Q1l2Pf/W7tMgkhwTo7hxsE6AY5Q= X-Received: by 2002:aa7:df97:0:b0:5af:758a:6934 with SMTP id 4fb4d7f45d1cf-5b7f0fc7f1amr8956337a12.0.1722893319128; Mon, 05 Aug 2024 14:28:39 -0700 (PDT) MIME-Version: 1.0 References: <20240804075619.20804-1-laoar.shao@gmail.com> In-Reply-To: <20240804075619.20804-1-laoar.shao@gmail.com> From: Linus Torvalds Date: Mon, 5 Aug 2024 14:28:21 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 0/9] Improve the copy of task comm To: Yafang Shao Cc: akpm@linux-foundation.org, ebiederm@xmission.com, alexei.starovoitov@gmail.com, rostedt@goodmis.org, catalin.marinas@arm.com, penguin-kernel@i-love.sakura.ne.jp, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, audit@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: E136C180002 X-Stat-Signature: wuqfife8zozaok7re8bbxh3wmmxeaq4g X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1722893322-861648 X-HE-Meta: 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 KQrA2UkA 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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 Sun, 4 Aug 2024 at 00:56, Yafang Shao wrote: > > There is a BUILD_BUG_ON() inside get_task_comm(), so when you use > get_task_comm(), it implies that the BUILD_BUG_ON() is necessary. Let's just remove that silly BUILD_BUG_ON(). I don't think it adds any value, and honestly, it really only makes this patch-series uglier when reasonable uses suddenly pointlessly need that double-underscore version.. So let's aim at (a) documenting that the last byte in 'tsk->comm{}' is always guaranteed to be NUL, so that the thing can always just be treated as a string. Yes, it may change under us, but as long as we know there is always a stable NUL there *somewhere*, we really really don't care. (b) removing __get_task_comm() entirely, and replacing it with a plain 'str*cpy*()' functions The whole (a) thing is a requirement anyway, since the *bulk* of tsk->comm really just seems to be various '%s' things in printk strings etc. And once we just admit that we can use the string functions, all the get_task_comm() stuff is just unnecessary. And yes, some people may want to use the strscpy_pad() function because they want to fill the whole destination buffer. But that's entirely about the *destination* use, not the tsk->comm[] source, so it has nothing to do with any kind of "get_task_comm()" logic, and it was always wrong to care about the buffer sizes magically matching. Hmm? Linus