From nobody Mon Oct 6 06:47:31 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 BC48D2D238B; Thu, 24 Jul 2025 12:36:50 +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=1753360612; cv=none; b=pCXLCpwvWG1J9CTYYdLgURSxzZCruVmQL8ecs7YRQGyjf3/pei33Go2NrvSYs7Y3WTH24N4V47ehw9cnKDsAtGbbuEA1WVQ19O/E1NPWJcOiSCqOfdTkrJQAA8Qd7j2C7k94qpF7Hnu+vVCm5VA3CsTdMcqjdfl0TGVE5s3lBak= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753360612; c=relaxed/simple; bh=ZTxbfBR4e9g+Vo8kn1KwzFv9oZCibHXpEedTrwXLllA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=rmhBZpsUZRS6/H24u0WDALz+8dwDAwOezpsnuzKER54F2TQOss5iBv74OXDGX+NhCJV3h512wF6OGHQFYEvY0PCH4CGGHzLOsNAIfvg3wQxclGpr0ou9uyqZoxTL+RA/c/U4D8gA7jwHCz4UOSH1+x5qYL2HbAteM4ZL4q68tzo= 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=YmObt6aa; 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="YmObt6aa" 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=Ay/n4segqzBtdJcxqD3V5D84mQe9aCStMnYXrz6ny88=; b=YmObt6aaSGJMlOElGiwShkA2s/ x+rR+nIVtETN4fxSYbthlIKDkyjCfgR7qOqA2UrOGd6LqO9gw+PYxxgZeFBICgr7qUdtBFjLfFM7W Nv6FYxDlDTRkKpz7GL0fSTbio5vcycsCc4PJA8PCHRR1bHBai76XHK/b43JKemwkCIWlhbbfMAkTb gqSIPF5a/3ltQT2Oof/c5JVFCWpFY3GVTi9kubC7jULyNgI/FYDBiLBzkTqvdzXSqfrewsSh5ATab kwkzlCsK1mZ1XhkC/u2qTga8BFUrn9aoaENc/c1pPMTM8oBR6w0dtJKqrpK08kecCVUjhPzt7lpqE YouuGFPg==; Received: from [223.233.78.24] (helo=localhost.localdomain) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1uevBm-003BPU-Nn; Thu, 24 Jul 2025 14:36:47 +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, linux-trace-kernel@vger.kernel.org, kees@kernel.org, torvalds@linux-foundation.org Subject: [PATCH v6 3/3] include: Set tsk->comm length to 64 bytes Date: Thu, 24 Jul 2025 18:06:12 +0530 Message-Id: <20250724123612.206110-4-bhupesh@igalia.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20250724123612.206110-1-bhupesh@igalia.com> References: <20250724123612.206110-1-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, we now use a 64-byte TASK_COMM_EXT_LEN and set the comm element inside 'task_struct' to the same length: struct task_struct { ..... char comm[TASK_COMM_EXT_LEN]; ..... }; where TASK_COMM_EXT_LEN is 64-bytes. Now, in order to maintain existing ABI, we ensure that: - Existing users of 'get_task_comm'/ 'set_task_comm' will get 'tsk->comm' truncated to a maximum of 'TASK_COMM_LEN' (16-bytes) to maintain ABI, - New / Modified users of 'get_task_comm'/ 'set_task_comm' will get 'tsk->comm' supported up to the maximum of 'TASK_COMM_EXT_LEN' (64-bytes). Note, that the existing users have not been modified to migrate to 'TASK_COMM_EXT_LEN', in case they have hard-coded expectations of dealing with only a 'TASK_COMM_LEN' long 'tsk->comm'. Signed-off-by: Bhupesh --- include/linux/sched.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 8bbd03f1b978..b6abb759292c 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, + TASK_COMM_EXT_LEN =3D 64, }; =20 extern void sched_tick(void); @@ -1159,7 +1160,7 @@ struct task_struct { * - logic inside set_task_comm() will ensure it is always NUL-terminat= ed and * zero-padded */ - char comm[TASK_COMM_LEN]; + char comm[TASK_COMM_EXT_LEN]; =20 struct nameidata *nameidata; =20 @@ -1954,7 +1955,7 @@ extern void kick_process(struct task_struct *tsk); =20 extern void __set_task_comm(struct task_struct *tsk, const char *from, boo= l exec); #define set_task_comm(tsk, from) ({ \ - BUILD_BUG_ON(sizeof(from) !=3D TASK_COMM_LEN); \ + BUILD_BUG_ON(sizeof(from) < TASK_COMM_LEN); \ __set_task_comm(tsk, from, false); \ }) =20 @@ -1974,6 +1975,10 @@ 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); \ + if ((sizeof(buf)) =3D=3D TASK_COMM_LEN) \ + buf[TASK_COMM_LEN - 1] =3D '\0'; \ + else \ + buf[TASK_COMM_EXT_LEN - 1] =3D '\0'; \ buf; \ }) =20 --=20 2.38.1