From nobody Thu Dec 18 03:20:33 2025 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) (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 CEFFB217647; Wed, 7 May 2025 11:05:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.97.179.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746615913; cv=none; b=VfSflbkwIBNxYw5jTMAYLH3KeJlBPlYPwAMCjZgnM3Q756f9rImMGXUMa5pfO2Mi6PFGEuM/+btDqlv9WSfQLXMHNYCDxSv4R/y87M4jnWDXiqNIJbWssTh/fOGbTOEpEeDOeTxvnW3jwNAYFX8afPjaDikPCyga3PW8ol9S6i0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746615913; c=relaxed/simple; bh=OOgluzoXjvHZLR2HjzqZH+NGY592izlc7i8Ve6dEhNs=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ifQ4wNn9CdhKTUtrRvVey05hFLgywMquYATCRVp8m0uk7T+H3alIN19e9+ZoA+eynKewGrIsoDVICWBe4654KzT+OxbSCra/HTA8v299sJYuKegGfrpeolZX0rF7SYfl+jD21lzhcUAJQIMNhBF72FSIRlH8E7KLoDF8plCJXwQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=IJ9uqSr9; arc=none smtp.client-ip=213.97.179.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="IJ9uqSr9" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=gTfNNksQy2E+ZtNstFehMQzC+wJ++X6RiLzY/QWMRNA=; b=IJ9uqSr9rFPG1mHRB12cq4yByj Mx/zCauO0XxO+S7x7YUDG/44QxjctCmeqpz7vEJ5O7VyyqdQrWTeZvTAkDS/t72+cIk8E0g+qi99i KDEngf63HRzoRyMiVN65nxhne6mcg4iON6vUX/wJGz+b8cM85S7rcHCXODaVklIRByFV6SDo1vrTJ ex6dx3RlXGK8dTEKI1lzCaLQjj6JUB1/KkuUqabtqyfQY1USrIbPQpO0X7lks9W9WWXeqroJAOICd rwSAkKbOjHpEJLo6LIlEkajdwMuvi9dev0q3SPt3ZAJ22jRKEm13klqZIF4b/sSwpX9ydk5nWHK/5 1RgX2Vxw==; Received: from [223.233.66.62] (helo=localhost.localdomain) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1uCcWU-004fhg-Et; Wed, 07 May 2025 13:05:05 +0200 From: Bhupesh To: akpm@linux-foundation.org Cc: bhupesh@igalia.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, oliver.sang@intel.com, lkp@intel.com, laoar.shao@gmail.com, pmladek@suse.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, alexei.starovoitov@gmail.com, andrii.nakryiko@gmail.com, mirq-linux@rere.qmqm.pl, peterz@infradead.org, willy@infradead.org, david@redhat.com, viro@zeniv.linux.org.uk, keescook@chromium.org, ebiederm@xmission.com, brauner@kernel.org, jack@suse.cz, mingo@redhat.com, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Subject: [PATCH v3 1/3] exec: Remove obsolete comments Date: Wed, 7 May 2025 16:34:42 +0530 Message-Id: <20250507110444.963779-2-bhupesh@igalia.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20250507110444.963779-1-bhupesh@igalia.com> References: <20250507110444.963779-1-bhupesh@igalia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Patch 3a3f61ce5e0b ("exec: Make sure task->comm is always NUL-terminated"), replaced 'strscpy_pad()' with 'memcpy()' implementations inside '__set_task_comm()'. However a few left-over comments are still there, which mention the usage of 'strscpy_pad()' inside '__set_task_comm()'. Remove those obsolete comments. While at it, also remove an obsolete comment regarding 'task_lock()' usage while handing 'task->comm'. Signed-off-by: Bhupesh --- include/linux/sched.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index f96ac1982893..cb219c6db179 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1159,10 +1159,8 @@ struct task_struct { * * - normally initialized begin_new_exec() * - set it with set_task_comm() - * - strscpy_pad() to ensure it is always NUL-terminated and + * - logic inside set_task_comm() will ensure it is always NUL-terminat= ed and * zero-padded - * - task_lock() to ensure the operation is atomic and the name is - * fully updated. */ char comm[TASK_COMM_LEN]; =20 @@ -1997,7 +1995,7 @@ extern void __set_task_comm(struct task_struct *tsk, = const char *from, bool exec * User space can randomly change their names anyway, so locking for rea= ders * 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 + * The logic inside __set_task_comm() should ensure that the task comm is * always NUL-terminated and zero-padded. Therefore the race condition b= etween * reader and writer is not an issue. * --=20 2.38.1 From nobody Thu Dec 18 03:20:33 2025 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) (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 C04AD220F4D; Wed, 7 May 2025 11:05:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.97.179.56 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746615918; cv=none; b=IDzXo8yCdbYUTjPjlvbopl+mT3HmyFdmSfnlW1/0i2ONEXC/r2B38GyJCA/e2wQUF4M7hSEqhF7Z7wx88aasegI9Z0KX2V9lW2tbTpAexXW6CshbWZTCiYlEn4cg9RWv9vebS/YKHLnVCmlYJVNLXPCPNlihwrWw/moc48qBeog= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746615918; c=relaxed/simple; bh=e3aGZP70jxUNb+/lCFUVUQ4+81xhoV5u73X0xieaeFA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=NltG/ftFJsn0Yx/v30cFc6AAomc7oTF1wRsp5d+NQ2DGEcZJn1ESxau4/nFS3gwAxBa+/2QNeRWh5J+ry33dVtLQ2q9Vzm3UWbxneLBSF+owz/G2+hze8TMw4avIXJ3B5RHdl+Q35Vr0Iai4Kb+d6CslexcrSIyKX4xL3ZkzqNU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=YiiUP5eQ; arc=none smtp.client-ip=213.97.179.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="YiiUP5eQ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=WDkvWa3TSuFgagk4tHSvnu3aN8dyFDkVfMiKuLfeTvc=; b=YiiUP5eQmiRvA58V2urS/zA0/i lrhuXgQKnAoXV0QlYLqB7dnloSUu6KsWBSpQUJIi9WtRqfYxnD5y/aDxXUEqtRElGBt1wjkRtxJfz 4II61sik1sB7z2u7cdwEnaESgdtdEHVAGIeHtU/qfe8myoWRXVzk+kd7TtRGWYvtj8Xjuqlx4/ivV /K1NyD/RZWnBduY0dymnxEkuJNIHplFhxhux5hWKuxI4i1BCejDjZysj26YBDmrk63IOi3tS85tN7 ltg9pe4l7aAxEL4752bP3qMgD8j3VlyZEljXAFj0uDAf2PK+URJm4n7TujpbZpNZYU6uG2Ov9/vfd pc3yyTdg==; Received: from [223.233.66.62] (helo=localhost.localdomain) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1uCcWa-004fhg-HR; Wed, 07 May 2025 13:05:11 +0200 From: Bhupesh To: akpm@linux-foundation.org Cc: bhupesh@igalia.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, oliver.sang@intel.com, lkp@intel.com, laoar.shao@gmail.com, pmladek@suse.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, alexei.starovoitov@gmail.com, andrii.nakryiko@gmail.com, mirq-linux@rere.qmqm.pl, peterz@infradead.org, willy@infradead.org, david@redhat.com, viro@zeniv.linux.org.uk, keescook@chromium.org, ebiederm@xmission.com, brauner@kernel.org, jack@suse.cz, mingo@redhat.com, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Subject: [PATCH v3 2/3] treewide: Switch memcpy() users of 'task->comm' to a more safer implementation Date: Wed, 7 May 2025 16:34:43 +0530 Message-Id: <20250507110444.963779-3-bhupesh@igalia.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20250507110444.963779-1-bhupesh@igalia.com> References: <20250507110444.963779-1-bhupesh@igalia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" As Linus mentioned in [1], currently we have several memcpy() use-cases which use 'current->comm' to copy the task name over to local copies. For an example: ... char comm[TASK_COMM_LEN]; memcpy(comm, current->comm, TASK_COMM_LEN); ... These should be modified so that we can later implement approaches to handle the task->comm's 16-byte length limitation (TASK_COMM_LEN) is a more modular way (follow-up patches do the same): ... char comm[TASK_COMM_LEN]; memcpy(comm, current->comm, TASK_COMM_LEN); comm[TASK_COMM_LEN - 1] =3D 0; ... The relevant 'memcpy()' users were identified using the following search pattern: $ git grep 'memcpy.*->comm\>' [1]. https://lore.kernel.org/all/CAHk-=3DwjAmmHUg6vho1KjzQi2=3DpsR30+CogFd4= aXrThr2gsiS4g@mail.gmail.com/ Signed-off-by: Bhupesh --- include/linux/coredump.h | 3 ++- include/trace/events/block.h | 5 +++++ include/trace/events/oom.h | 1 + include/trace/events/osnoise.h | 1 + include/trace/events/sched.h | 13 +++++++++++++ include/trace/events/signal.h | 1 + include/trace/events/task.h | 2 ++ 7 files changed, 25 insertions(+), 1 deletion(-) diff --git a/include/linux/coredump.h b/include/linux/coredump.h index 77e6e195d1d6..058ae3f2bec8 100644 --- a/include/linux/coredump.h +++ b/include/linux/coredump.h @@ -53,7 +53,8 @@ extern void do_coredump(const kernel_siginfo_t *siginfo); do { \ char comm[TASK_COMM_LEN]; \ /* This will always be NUL terminated. */ \ - memcpy(comm, current->comm, sizeof(comm)); \ + memcpy(comm, current->comm, TASK_COMM_LEN); \ + comm[TASK_COMM_LEN] =3D '\0'; \ printk_ratelimited(Level "coredump: %d(%*pE): " Format "\n", \ task_tgid_vnr(current), (int)strlen(comm), comm, ##__VA_ARGS__); \ } while (0) \ diff --git a/include/trace/events/block.h b/include/trace/events/block.h index bd0ea07338eb..94a941ac2034 100644 --- a/include/trace/events/block.h +++ b/include/trace/events/block.h @@ -214,6 +214,7 @@ DECLARE_EVENT_CLASS(block_rq, blk_fill_rwbs(__entry->rwbs, rq->cmd_flags); __get_str(cmd)[0] =3D '\0'; memcpy(__entry->comm, current->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; ), =20 TP_printk("%d,%d %s %u (%s) %llu + %u %s,%u,%u [%s]", @@ -352,6 +353,7 @@ DECLARE_EVENT_CLASS(block_bio, __entry->nr_sector =3D bio_sectors(bio); blk_fill_rwbs(__entry->rwbs, bio->bi_opf); memcpy(__entry->comm, current->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; ), =20 TP_printk("%d,%d %s %llu + %u [%s]", @@ -439,6 +441,7 @@ TRACE_EVENT(block_plug, =20 TP_fast_assign( memcpy(__entry->comm, current->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; ), =20 TP_printk("[%s]", __entry->comm) @@ -458,6 +461,7 @@ DECLARE_EVENT_CLASS(block_unplug, TP_fast_assign( __entry->nr_rq =3D depth; memcpy(__entry->comm, current->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; ), =20 TP_printk("[%s] %d", __entry->comm, __entry->nr_rq) @@ -509,6 +513,7 @@ TRACE_EVENT(block_split, __entry->new_sector =3D new_sector; blk_fill_rwbs(__entry->rwbs, bio->bi_opf); memcpy(__entry->comm, current->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; ), =20 TP_printk("%d,%d %s %llu / %llu [%s]", diff --git a/include/trace/events/oom.h b/include/trace/events/oom.h index 9f0a5d1482c4..a5641ed4285f 100644 --- a/include/trace/events/oom.h +++ b/include/trace/events/oom.h @@ -24,6 +24,7 @@ TRACE_EVENT(oom_score_adj_update, TP_fast_assign( __entry->pid =3D task->pid; memcpy(__entry->comm, task->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->oom_score_adj =3D task->signal->oom_score_adj; ), =20 diff --git a/include/trace/events/osnoise.h b/include/trace/events/osnoise.h index 3f4273623801..0321b3f8d532 100644 --- a/include/trace/events/osnoise.h +++ b/include/trace/events/osnoise.h @@ -117,6 +117,7 @@ TRACE_EVENT(thread_noise, =20 TP_fast_assign( memcpy(__entry->comm, t->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D t->pid; __entry->start =3D start; __entry->duration =3D duration; diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h index 8994e97d86c1..3126d44c43ee 100644 --- a/include/trace/events/sched.h +++ b/include/trace/events/sched.h @@ -26,6 +26,7 @@ TRACE_EVENT(sched_kthread_stop, =20 TP_fast_assign( memcpy(__entry->comm, t->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D t->pid; ), =20 @@ -153,6 +154,7 @@ DECLARE_EVENT_CLASS(sched_wakeup_template, =20 TP_fast_assign( memcpy(__entry->comm, p->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D p->pid; __entry->prio =3D p->prio; /* XXX SCHED_DEADLINE */ __entry->target_cpu =3D task_cpu(p); @@ -238,10 +240,12 @@ TRACE_EVENT(sched_switch, =20 TP_fast_assign( memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->prev_pid =3D prev->pid; __entry->prev_prio =3D prev->prio; __entry->prev_state =3D __trace_sched_switch_state(preempt, prev_state, = prev); memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN); + __entry->next_comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->next_pid =3D next->pid; __entry->next_prio =3D next->prio; /* XXX SCHED_DEADLINE */ @@ -285,6 +289,7 @@ TRACE_EVENT(sched_migrate_task, =20 TP_fast_assign( memcpy(__entry->comm, p->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D p->pid; __entry->prio =3D p->prio; /* XXX SCHED_DEADLINE */ __entry->orig_cpu =3D task_cpu(p); @@ -310,6 +315,7 @@ DECLARE_EVENT_CLASS(sched_process_template, =20 TP_fast_assign( memcpy(__entry->comm, p->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D p->pid; __entry->prio =3D p->prio; /* XXX SCHED_DEADLINE */ ), @@ -356,6 +362,7 @@ TRACE_EVENT(sched_process_wait, =20 TP_fast_assign( memcpy(__entry->comm, current->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D pid_nr(pid); __entry->prio =3D current->prio; /* XXX SCHED_DEADLINE */ ), @@ -382,8 +389,10 @@ TRACE_EVENT(sched_process_fork, =20 TP_fast_assign( memcpy(__entry->parent_comm, parent->comm, TASK_COMM_LEN); + __entry->parent_comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->parent_pid =3D parent->pid; memcpy(__entry->child_comm, child->comm, TASK_COMM_LEN); + __entry->child_comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->child_pid =3D child->pid; ), =20 @@ -480,6 +489,7 @@ DECLARE_EVENT_CLASS_SCHEDSTAT(sched_stat_template, =20 TP_fast_assign( memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D tsk->pid; __entry->delay =3D delay; ), @@ -538,6 +548,7 @@ DECLARE_EVENT_CLASS(sched_stat_runtime, =20 TP_fast_assign( memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D tsk->pid; __entry->runtime =3D runtime; ), @@ -570,6 +581,7 @@ TRACE_EVENT(sched_pi_setprio, =20 TP_fast_assign( memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D tsk->pid; __entry->oldprio =3D tsk->prio; __entry->newprio =3D pi_task ? @@ -595,6 +607,7 @@ TRACE_EVENT(sched_process_hang, =20 TP_fast_assign( memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D tsk->pid; ), =20 diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h index 1db7e4b07c01..7f490e553db5 100644 --- a/include/trace/events/signal.h +++ b/include/trace/events/signal.h @@ -68,6 +68,7 @@ TRACE_EVENT(signal_generate, __entry->sig =3D sig; TP_STORE_SIGINFO(__entry, info); memcpy(__entry->comm, task->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->pid =3D task->pid; __entry->group =3D group; __entry->result =3D result; diff --git a/include/trace/events/task.h b/include/trace/events/task.h index af535b053033..4ddf21b69372 100644 --- a/include/trace/events/task.h +++ b/include/trace/events/task.h @@ -22,6 +22,7 @@ TRACE_EVENT(task_newtask, TP_fast_assign( __entry->pid =3D task->pid; memcpy(__entry->comm, task->comm, TASK_COMM_LEN); + __entry->comm[TASK_COMM_LEN - 1] =3D '\0'; __entry->clone_flags =3D clone_flags; __entry->oom_score_adj =3D task->signal->oom_score_adj; ), @@ -45,6 +46,7 @@ TRACE_EVENT(task_rename, =20 TP_fast_assign( memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN); + entry->oldcomm[TASK_COMM_LEN - 1] =3D '\0'; strscpy(entry->newcomm, comm, TASK_COMM_LEN); __entry->oom_score_adj =3D task->signal->oom_score_adj; ), --=20 2.38.1 From nobody Thu Dec 18 03:20:33 2025 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) (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 BA528236440; 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Received: from [223.233.66.62] (helo=localhost.localdomain) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1uCcWg-004fhg-Ha; Wed, 07 May 2025 13:05:17 +0200 From: Bhupesh To: akpm@linux-foundation.org Cc: bhupesh@igalia.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, oliver.sang@intel.com, lkp@intel.com, laoar.shao@gmail.com, pmladek@suse.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, alexei.starovoitov@gmail.com, andrii.nakryiko@gmail.com, mirq-linux@rere.qmqm.pl, peterz@infradead.org, willy@infradead.org, david@redhat.com, viro@zeniv.linux.org.uk, keescook@chromium.org, ebiederm@xmission.com, brauner@kernel.org, jack@suse.cz, mingo@redhat.com, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Subject: [PATCH v3 3/3] exec: Add support for 64 byte 'tsk->real_comm' Date: Wed, 7 May 2025 16:34:44 +0530 Message-Id: <20250507110444.963779-4-bhupesh@igalia.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20250507110444.963779-1-bhupesh@igalia.com> References: <20250507110444.963779-1-bhupesh@igalia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Historically due to the 16-byte length of TASK_COMM_LEN, the users of 'tsk->comm' are restricted to use a fixed-size target buffer also of TASK_COMM_LEN for 'memcpy()' like use-cases. To fix the same, Linus suggested in [1] that we can add the following union inside 'task_struct': union { char comm[TASK_COMM_LEN]; char real_comm[REAL_TASK_COMM_LEN]; }; and then modify '__set_task_comm()' to pass 'tsk->real_comm' to the existing users. This would mean that: (1) The old common pattern of just printing with '%s' and tsk->comm would just continue to work (as it is): pr_alert("BUG: Bad page state in process %s pfn:%05lx\n", current->comm, page_to_pfn(page)); (2) And, the memcpy() users of 'tsk->comm' would need to be made more stable by ensuring that the destination buffer always has a closing NUL character (done already in the preceding patch in this series). So, eventually: - users who want the existing 'TASK_COMM_LEN' behavior will get it (existing ABIs would continue to work), - users who just print out 'tsk->comm' as a string will get the longer new "real comm", - users who do 'sizeof(->comm)' will continue to get the old value because of the union. [1]. https://lore.kernel.org/all/CAHk-=3DwjAmmHUg6vho1KjzQi2=3DpsR30+CogFd4= aXrThr2gsiS4g@mail.gmail.com Signed-off-by: Bhupesh --- fs/exec.c | 6 +++--- include/linux/sched.h | 8 ++++++-- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 8e4ea5f1e64c..2b2f2dacc013 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1190,11 +1190,11 @@ static int unshare_sighand(struct task_struct *me) */ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) { - size_t len =3D min(strlen(buf), sizeof(tsk->comm) - 1); + size_t len =3D min(strlen(buf), sizeof(tsk->real_comm) - 1); =20 trace_task_rename(tsk, buf); - memcpy(tsk->comm, buf, len); - memset(&tsk->comm[len], 0, sizeof(tsk->comm) - len); + memcpy(tsk->real_comm, buf, len); + memset(&tsk->real_comm[len], 0, sizeof(tsk->real_comm) - len); perf_event_comm(tsk, exec); } =20 diff --git a/include/linux/sched.h b/include/linux/sched.h index cb219c6db179..2744d90badf1 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -317,6 +317,7 @@ struct user_event_mm; */ enum { TASK_COMM_LEN =3D 16, + REAL_TASK_COMM_LEN =3D 64, }; =20 extern void sched_tick(void); @@ -1162,7 +1163,10 @@ struct task_struct { * - logic inside set_task_comm() will ensure it is always NUL-terminat= ed and * zero-padded */ - char comm[TASK_COMM_LEN]; + union { + char comm[TASK_COMM_LEN]; + char real_comm[REAL_TASK_COMM_LEN]; + }; =20 struct nameidata *nameidata; =20 @@ -2005,7 +2009,7 @@ extern void __set_task_comm(struct task_struct *tsk, = const char *from, bool exec */ #define get_task_comm(buf, tsk) ({ \ BUILD_BUG_ON(sizeof(buf) < TASK_COMM_LEN); \ - strscpy_pad(buf, (tsk)->comm); \ + strscpy_pad(buf, (tsk)->real_comm); \ buf; \ }) =20 --=20 2.38.1