From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D83E18858C for ; Wed, 6 Nov 2024 01:13:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730855609; cv=none; b=Qf/1L/YMnhEiwuXRlVLxDCpfCCQcW+vjQCZZkiEPAOMDIvkMAkQgnWFbTZ3EeCxsI+MGIJkUcEfrOWFYbZ9Ay+el3BonWHPrvjrlD6KysSSoV3SM+/6pehXJxackTjpgZ1dT/L25Yvt0NZf8Nb4YjkKaJlZ7Pu3cStn0W0oarOE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730855609; c=relaxed/simple; bh=8oGr3Zf0UOeQTWeUIm6AChLX0XIns2fe3S7nyl2lvaQ=; h=Date:To:From:Subject:Message-Id; b=n5Jt+NxQG4YKY4lRG+iX8ZL+zbR6lJpS2aqnC4S0i3+prkvaN2MaY2DLLD9NqydZ5staDfN8ffleyRbnF3DHNTC2WuTROEjtMbzoLHqca4SKHlYxhfRb8oGm2ND2/AhFuxJ4np4HJlPRr1xDui0GksdrJGv8WTi37U2GTltcPuE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Cu3AbdUv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Cu3AbdUv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1027C4CECF; Wed, 6 Nov 2024 01:13:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1730855609; bh=8oGr3Zf0UOeQTWeUIm6AChLX0XIns2fe3S7nyl2lvaQ=; h=Date:To:From:Subject:From; b=Cu3AbdUvX63Muy+7bzZuTXOVaMSg+g2hZ3HrissnekN2Aa9LkkYlP6Q5qtjQ4K8pA Zk8xTcP6xm0/zlshTnNUnA9SMqURZ6rpdu2D1W6Lm8CZSMx45FIOrghNJevmXBXgtf Lf/EXmUjOzF7VAX2Bz7jPlZeGF11W2y7VGVW/pts= Date: Tue, 05 Nov 2024 17:13:28 -0800 To: mm-commits@vger.kernel.org,willy@infradead.org,viro@zeniv.linux.org.uk,tzimmermann@suse.de,torvalds@linux-foundation.org,stephen.smalley.work@gmail.com,serge@hallyn.com,rostedt@goodmis.org,qmo@kernel.org,penguin-kernel@I-love.SAKURA.ne.jp,paul@paul-moore.com,omosnace@redhat.com,mripard@kernel.org,matus.jokay@stuba.sk,maarten.lankhorst@linux.intel.com,keescook@chromium.org,justinstitt@google.com,jmorris@namei.org,jack@suse.cz,horms@kernel.org,eparis@redhat.com,ebiederm@xmission.com,daniel.vetter@ffwll.ch,catalin.marinas@arm.com,brauner@kernel.org,andy.shevchenko@gmail.com,alx@kernel.org,alexei.starovoitov@gmail.com,airlied@gmail.com,laoar.shao@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-nonmm-stable] get-rid-of-__get_task_comm.patch removed from -mm tree Message-Id: <20241106011328.F1027C4CECF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: get rid of __get_task_comm() has been removed from the -mm tree. Its filename was get-rid-of-__get_task_comm.patch This patch was dropped because it was merged into the mm-nonmm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Yafang Shao Subject: get rid of __get_task_comm() Date: Mon, 7 Oct 2024 22:49:05 +0800 Patch series "Improve the copy of task comm", v8. Using {memcpy,strncpy,strcpy,kstrdup} to copy the task comm relies on the length of task comm. Changes in the task comm could result in a destination string that is overflow. Therefore, we should explicitly ensure the destination string is always NUL-terminated, regardless of the task comm. This approach will facilitate future extensions to the task comm. As suggested by Linus [0], we can identify all relevant code with the following git grep command: git grep 'memcpy.*->comm\>' git grep 'kstrdup.*->comm\>' git grep 'strncpy.*->comm\>' git grep 'strcpy.*->comm\>' PATCH #2~#4: memcpy PATCH #5~#6: kstrdup PATCH #7: strcpy Please note that strncpy() is not included in this series as it is being tracked by another effort. [1] This patch (of 7): We want to eliminate the use of __get_task_comm() for the following reasons: - The task_lock() is unnecessary Quoted from Linus [0]: : Since user space can randomly change their names anyway, using locking : was always wrong for readers (for writers it probably does make sense : to have some lock - although practically speaking nobody cares there : either, but at least for a writer some kind of race could have : long-term mixed results Link: https://lkml.kernel.org/r/20241007144911.27693-1-laoar.shao@gmail.com Link: https://lkml.kernel.org/r/20241007144911.27693-2-laoar.shao@gmail.com Link: https://lore.kernel.org/all/CAHk-=wivfrF0_zvf+oj6==Sh=-npJooP8chLPEfaFV0oNYTTBA@mail.gmail.com [0] Link: https://lore.kernel.org/all/CAHk-=whWtUC-AjmGJveAETKOMeMFSTwKwu99v7+b6AyHMmaDFA@mail.gmail.com/ Link: https://lore.kernel.org/all/CAHk-=wjAmmHUg6vho1KjzQi2=psR30+CogFd4aXrThr2gsiS4g@mail.gmail.com/ [0] Link: https://github.com/KSPP/linux/issues/90 [1] Signed-off-by: Yafang Shao Suggested-by: Linus Torvalds Cc: Alexander Viro Cc: Christian Brauner Cc: Jan Kara Cc: Eric Biederman Cc: Kees Cook Cc: Alexei Starovoitov Cc: Matus Jokay Cc: Alejandro Colomar Cc: "Serge E. Hallyn" Cc: Catalin Marinas Cc: Justin Stitt Cc: Steven Rostedt (Google) Cc: Tetsuo Handa Cc: Andy Shevchenko Cc: Daniel Vetter Cc: David Airlie Cc: Eric Paris Cc: James Morris Cc: Maarten Lankhorst Cc: Matthew Wilcox Cc: Maxime Ripard Cc: Ondrej Mosnacek Cc: Paul Moore Cc: Quentin Monnet Cc: Simon Horman Cc: Stephen Smalley Cc: Thomas Zimmermann Signed-off-by: Andrew Morton --- fs/exec.c | 10 ---------- fs/proc/array.c | 2 +- include/linux/sched.h | 28 ++++++++++++++++++++++------ kernel/kthread.c | 2 +- 4 files changed, 24 insertions(+), 18 deletions(-) --- a/fs/exec.c~get-rid-of-__get_task_comm +++ a/fs/exec.c @@ -1189,16 +1189,6 @@ static int unshare_sighand(struct task_s return 0; } -char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) -{ - task_lock(tsk); - /* Always NUL terminated and zero-padded */ - strscpy_pad(buf, tsk->comm, buf_size); - task_unlock(tsk); - return buf; -} -EXPORT_SYMBOL_GPL(__get_task_comm); - /* * These functions flushes out all traces of the currently running executable * so that a new one can be started --- a/fs/proc/array.c~get-rid-of-__get_task_comm +++ a/fs/proc/array.c @@ -109,7 +109,7 @@ void proc_task_name(struct seq_file *m, else if (p->flags & PF_KTHREAD) get_kthread_comm(tcomm, sizeof(tcomm), p); else - __get_task_comm(tcomm, sizeof(tcomm), p); + get_task_comm(tcomm, p); if (escape) seq_escape_str(m, tcomm, ESCAPE_SPACE | ESCAPE_SPECIAL, "\n\\"); --- a/include/linux/sched.h~get-rid-of-__get_task_comm +++ a/include/linux/sched.h @@ -1121,9 +1121,12 @@ struct task_struct { /* * executable name, excluding path. * - * - normally initialized setup_new_exec() - * - access it with [gs]et_task_comm() - * - lock it with task_lock() + * - normally initialized begin_new_exec() + * - set it with set_task_comm() + * - strscpy_pad() to ensure it is always NUL-terminated and + * zero-padded + * - task_lock() to ensure the operation is atomic and the name is + * fully updated. */ char comm[TASK_COMM_LEN]; @@ -1938,10 +1941,23 @@ static inline void set_task_comm(struct __set_task_comm(tsk, from, false); } -extern char *__get_task_comm(char *to, size_t len, struct task_struct *tsk); +/* + * - Why not use task_lock()? + * User space can randomly change their names anyway, so locking for readers + * doesn't make sense. For writers, locking is probably necessary, as a race + * condition could lead to long-term mixed results. + * The strscpy_pad() in __set_task_comm() can ensure that the task comm is + * always NUL-terminated and zero-padded. Therefore the race condition between + * reader and writer is not an issue. + * + * - BUILD_BUG_ON() can help prevent the buf from being truncated. + * Since the callers don't perform any return value checks, this safeguard is + * necessary. + */ #define get_task_comm(buf, tsk) ({ \ - BUILD_BUG_ON(sizeof(buf) != TASK_COMM_LEN); \ - __get_task_comm(buf, sizeof(buf), tsk); \ + BUILD_BUG_ON(sizeof(buf) < TASK_COMM_LEN); \ + strscpy_pad(buf, (tsk)->comm); \ + buf; \ }) #ifdef CONFIG_SMP --- a/kernel/kthread.c~get-rid-of-__get_task_comm +++ a/kernel/kthread.c @@ -101,7 +101,7 @@ void get_kthread_comm(char *buf, size_t struct kthread *kthread = to_kthread(tsk); if (!kthread || !kthread->full_name) { - __get_task_comm(buf, buf_size, tsk); + strscpy(buf, tsk->comm, buf_size); return; } _ Patches currently in -mm which might be from laoar.shao@gmail.com are