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AJvYcCU+LBl8WL7vMG8PgqcDZ1ImoXbdrhSvYlr0cZCavDZkOLGTxEEIbSsdT3QF3OOSxazLGed2HthAUfp/dgfZBopRaCU= X-Gm-Message-State: AOJu0Yw80fMRXpva0PG5naHoXpPCRZcVsIUD/AnlANIMqOTG0+VWz1L7 YnFrjWnV6tFKwPlqyq2cr8IRCdlhzhjzFqscB7TbFUuqWafNP8XvkCvM2fatf9DrKdu9Pi2nG7S z/rYzPJ0djpEI0XILytpDTFceKo8= X-Google-Smtp-Source: AGHT+IF5UmpKUFOnvoAK9lYxcwohmtfgqa1lFzGyA8Akl+YSskrOYOXqexc6VvI8Xmv0jJTGVagDPu5fB/SRGumTpvw= X-Received: by 2002:a05:6214:2425:b0:6b7:944f:3cef with SMTP id 6a1803df08f44-6bb55aa2fc3mr125032596d6.44.1722253564270; Mon, 29 Jul 2024 04:46:04 -0700 (PDT) MIME-Version: 1.0 References: <20240729023719.1933-1-laoar.shao@gmail.com> <87bk2gzgu0.fsf@intel.com> In-Reply-To: <87bk2gzgu0.fsf@intel.com> From: Yafang Shao Date: Mon, 29 Jul 2024 19:45:27 +0800 Message-ID: Subject: Re: [PATCH resend v4 00/11] Improve the copy of task comm To: Jani Nikula Cc: akpm@linux-foundation.org, torvalds@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" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 5275A14000C X-Rspamd-Server: rspam01 X-Stat-Signature: qow4r8wh49yz65ar6oju1rhzpga7fjhr X-HE-Tag: 1722253565-419268 X-HE-Meta: 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 oWTtMmr3 LfUVAZ2gZ1aw6ik54YBBg0iON0BuU7Pm/J+p9CP74mY2jTxN2FYe4CIKq3i7FAKHVU2iV7hjo4nxBQut+tPrvkw//9XLnEI+BxA+BSiOk7B4zJzXK6ICmqh7CPuHWNPUtkeLH+zUIkarVHMjw/yRBtAJZmsBNLvmtlzOPNiLK+mPmjC+iqpG69VxARe8aG8tewqkR3QBd2eqosUo8kgxRsF0ByZdOuyBkGjvAYPx1ou9IT/IG66n+DGVPoNBu0mi6lAEmCKvUPEl4lizwvUc3DosZz8aOw760aLgt3mljSVyMFcF5eALnb3dHsNcvmZo543jYEgsttUwhZkvkcu0itc81sMmzI/aH7RGYtSmpsKa0Txznh7VO+V6HgVdN1ujElsHxZMlya78vx7Fu47oovcMA6dIh/gG9R5sDQKozFSQ5DPzF4ea0aIwosn1nvjJesdEE X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, 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 Mon, Jul 29, 2024 at 5:29=E2=80=AFPM Jani Nikula wrote: > > On Mon, 29 Jul 2024, Yafang Shao wrote: > > Hello Andrew, > > > > Is it appropriate for you to apply this to the mm tree? > > > > Using {memcpy,strncpy,strcpy,kstrdup} to copy the task comm relies on t= he > > length of task comm. Changes in the task comm could result in a destina= tion > > string that is overflow. Therefore, we should explicitly ensure the des= tination > > string is always NUL-terminated, regardless of the task comm. This appr= oach > > will facilitate future extensions to the task comm. > > Why are we normalizing calling double-underscore prefixed functions all > over the place? i.e. __get_task_comm(). > > get_task_comm() is widely used. At a glance, looks like it could be used > in many of the patches here too. 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. However, we don't want to impose this restriction on code where the length can be dynamically changed. One use case of get_task_comm() is in code that has already exposed the length to userspace. In such cases, we specifically add the BUILD_BUG_ON() to prevent developers from changing it. For more information, see commit 95af469c4f60 ("fs/binfmt_elf: replace open-coded string copy with get_task_comm"). --=20 Regards Yafang