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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4606f20e77asm8584369f8f.0.2026.06.12.11.53.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Jun 2026 11:53:31 -0700 (PDT) Date: Fri, 12 Jun 2026 19:53:30 +0100 From: David Laight To: =?UTF-8?B?QW5kcsOp?= Almeida Cc: Peter Zijlstra , Juri Lelli , Vincent Guittot , Steven Rostedt , Christian Brauner , Kees Cook , Shuah Khan , willy@infradead.org, mathieu.desnoyers@efficios.com, Linus Torvalds , akpm@linux-foundation.org, Yafang Shao , andrii.nakryiko@gmail.com, arnaldo.melo@gmail.com, Petr Mladek , linux-kernel@vger.kernel.org, kernel-dev@igalia.com, linux-mm@kvack.org, linux-api@vger.kernel.org Subject: Re: [PATCH v3 3/7] treewide: Replace memcpy(..., current->comm) with copy_task_comm() Message-ID: <20260612195330.1653d041@pumpkin> In-Reply-To: <20260612-tonyk-long_name-v3-3-7989b66e8a99@igalia.com> References: <20260612-tonyk-long_name-v3-0-7989b66e8a99@igalia.com> <20260612-tonyk-long_name-v3-3-7989b66e8a99@igalia.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: BDAAE180002 X-Rspam-User: X-Stat-Signature: zhcrntb5m46fs49f7h3dm4yp5wqtdghk X-HE-Tag: 1781290413-246532 X-HE-Meta: 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 bZgMATC8 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 12 Jun 2026 13:20:16 -0300 Andr=C3=A9 Almeida wrote: > In order to increase the size of current->comm[] and to avoid breaking any > existing code, replace memcpy() with copy_task_comm(). This new function > makes sure that the copy is NUL terminated. This is crucial given that the > source buffer might be larger than the destination buffer and could > truncate the NUL character out of it. Aren't you re-inventing get_task_comm() that the previous patch removed? ... > +/* > + * Copy task name to a buffer. Final result is always a NUL-terminated s= tring. > + */ > +#define copy_task_comm(dst, tsk, len) \ > +{ \ > + const char *_src =3D (tsk)->comm; \ > + size_t _dst_len =3D len + __must_be_array(dst), If you are using __must_be_array() then why not use sizeof to get the _dst_= len? > + _src_len =3D sizeof(_src); \ Isn't sizeof(_src) just the size of a pointer? You need to use sizeof (tsk)->comm > + char *_dst =3D dst; \ > + \ > + if (_dst_len <=3D _src_len) { \ > + memcpy(_dst, _src, _dst_len); \ > + dst[_dst_len - 1] =3D '\0'; \ If the lengths are equal you don't need to write the '\0'. (and they should really both be compile time constants.) > + } else { \ > + strscpy_pad(_dst, _src, _dst_len); \ > + } \ If you do the memcpy() the bytes after the first '\0' aren't guaranteed to be '\0' - then can be random (usually part of an old version of the task na= me). So I'm not sure the strscpy_pad() path is needed. The most you might want to do is memset() the extra bytes. But are there ever any???? There will be code that copies the task->comm to a short buffer, but are there any places where it actually gets copied to a longer one - if so why? David