From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C898FC54FAA for ; Wed, 28 Aug 2024 13:57:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C660C6B0082; Wed, 28 Aug 2024 09:57:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BEF626B0083; Wed, 28 Aug 2024 09:57:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A693D6B0085; Wed, 28 Aug 2024 09:57:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 89B3E6B0082 for ; Wed, 28 Aug 2024 09:57:38 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 3977FA1FD9 for ; Wed, 28 Aug 2024 13:57:38 +0000 (UTC) X-FDA: 82501806996.15.FDC0056 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf25.hostedemail.com (Postfix) with ESMTP id D6F86A0015 for ; Wed, 28 Aug 2024 13:57:34 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=EbjLpfkN; spf=pass (imf25.hostedemail.com: domain of kees@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724853368; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=KI1oTlojnDTFFvbh5Hx5McLbiLYOK54J4Jn4cG7YzqY=; b=Bgufo30A9vgL2kL5+vcNn1WQla/DA0fRuHa3GvdKIv81OyvnT9RRG+VS+pX3fnvIReJCnC WF7cnsISqYaAyaSX5SYItnq7SQQgqM2TrVkZzcJTTzci3/LZnr6uZbg7MXRAbM/QG18yJQ u3JCOnwj/LKOdZg5Y3KApsHGJVqQ9mk= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724853368; a=rsa-sha256; cv=none; b=ubAGaoabzTUpRhAPOebmV2/AzE+eFxxvaAMG3iQwqEZh97flgXN4NCOUTG/RqGb1SUKDL+ PD3LNhet+lfB66iR4ByETzbPvOgEULVSXkMhEb2ArTlPoDPNN0wIRYt3KWVH+rG+yq7eIb UKgLkqY5pL0ql3jFzcIlsu79jEfQkow= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=EbjLpfkN; spf=pass (imf25.hostedemail.com: domain of kees@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id CED6FCE1813; Wed, 28 Aug 2024 13:57:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 716F8C5FB24; Wed, 28 Aug 2024 13:48:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724852918; bh=TFXHpYUbMPU1PBJdBGzhBTwFtAf9olUiwemN+xYfsaI=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=EbjLpfkNlvuKmapZ4irEc3+VoB7uNdRFIRrm37fZuyRc+hVMgA7reiu+oN5SrtH3L r5aLX0kCDbqvYUq/ujIE6rw/uu06Bt8oj9Hu3IKc0vGDwjC6fnE6vBD3dN9YNxQU8u 86Jxn9AehGCVE3LJBYwEIM2zAL48oXK+oLk4itMPso5Iz3c4nsCNfnEMtSE+18I/xd dEAuNkIPUKy9qd7cUdbKJLBVMrTgzuXOGogCTlVmiTQFwD7hn+LA/8kxfBjngnteo+ RG5H8USGaa8sS94tdIcVvfhl5sQn6YRvK++Lwf+dnnbWq/xtWKAknb2oyJmTD/thI0 PmekGQbSXjv1Q== Date: Wed, 28 Aug 2024 06:48:39 -0700 From: Kees Cook To: Yafang Shao , Alejandro Colomar CC: akpm@linux-foundation.org, torvalds@linux-foundation.org, justinstitt@google.com, 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, Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Matus Jokay , "Serge E. Hallyn" Subject: Re: [PATCH v8 1/8] Get rid of __get_task_comm() User-Agent: K-9 Mail for Android In-Reply-To: References: <20240828030321.20688-1-laoar.shao@gmail.com> <20240828030321.20688-2-laoar.shao@gmail.com> Message-ID: <7839453E-CA06-430A-A198-92EB906F94D9@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: D6F86A0015 X-Stat-Signature: bwoaot43ee3nna37h4ak8i6hu3ft6gko X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1724853454-666496 X-HE-Meta: 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 fSbRoeXC 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 August 28, 2024 6:40:35 AM PDT, Yafang Shao = wrote: >On Wed, Aug 28, 2024 at 8:58=E2=80=AFPM Alejandro Colomar wrote: >> >> On Wed, Aug 28, 2024 at 12:15:40PM GMT, Alejandro Colomar wrote: >> > Hi Yafang, >> > >> > On Wed, Aug 28, 2024 at 11:03:14AM GMT, Yafang Shao wrote: >> > > 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 >> > > >> > > - The BUILD_BUG_ON() doesn't add any value >> > > The only requirement is to ensure that the destination buffer is = a valid >> > > array=2E >> > > >> > > - Zeroing is not necessary in current use cases >> > > To avoid confusion, we should remove it=2E Moreover, not zeroing = could >> > > potentially make it easier to uncover bugs=2E If the caller needs= a >> > > zero-padded task name, it should be explicitly handled at the cal= l site=2E >> > > >> > > Suggested-by: Linus Torvalds >> > > Link: https://lore=2Ekernel=2Eorg/all/CAHk-=3DwivfrF0_zvf+oj6=3D=3D= Sh=3D-npJooP8chLPEfaFV0oNYTTBA@mail=2Egmail=2Ecom [0] >> > > Link: https://lore=2Ekernel=2Eorg/all/CAHk-=3DwhWtUC-AjmGJveAETKOMe= MFSTwKwu99v7+b6AyHMmaDFA@mail=2Egmail=2Ecom/ >> > > Suggested-by: Alejandro Colomar >> > > Link: https://lore=2Ekernel=2Eorg/all/2jxak5v6dfxlpbxhpm3ey7oup4g2l= nr3ueurfbosf5wdo65dk4@srb3hsk72zwq >> > > Signed-off-by: Yafang Shao >> > > 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=2E Hallyn" >> > > --- >> > > fs/exec=2Ec | 10 ---------- >> > > fs/proc/array=2Ec | 2 +- >> > > include/linux/sched=2Eh | 32 ++++++++++++++++++++++++++------ >> > > kernel/kthread=2Ec | 2 +- >> > > 4 files changed, 28 insertions(+), 18 deletions(-) >> > > >> > >> > [=2E=2E=2E] >> > >> > > diff --git a/include/linux/sched=2Eh b/include/linux/sched=2Eh >> > > index f8d150343d42=2E=2Ec40b95a79d80 100644 >> > > --- a/include/linux/sched=2Eh >> > > +++ b/include/linux/sched=2Eh >> > >> > [=2E=2E=2E] >> > >> > > @@ -1914,10 +1917,27 @@ static inline void set_task_comm(struct tas= k_struct *tsk, const char *from) >> > > __set_task_comm(tsk, from, false); >> > > } >> > > >> > > -extern char *__get_task_comm(char *to, size_t len, struct task_str= uct *tsk); >> > > +/* >> > >> > [=2E=2E=2E] >> > >> > > + * - ARRAY_SIZE() can help ensure that @buf is indeed an array=2E >> > > + */ >> > > #define get_task_comm(buf, tsk) ({ \ >> > > - BUILD_BUG_ON(sizeof(buf) !=3D TASK_COMM_LEN); \ >> > > - __get_task_comm(buf, sizeof(buf), tsk); \ >> > > + strscpy(buf, (tsk)->comm, ARRAY_SIZE(buf)); \ >> > >> > I see that there's a two-argument macro >> > >> > #define strscpy(dst, src) sized_strscpy(dst, src, sizeof(= dst)) >> > >> > which is used in patch 2/8 >> > >> > diff --git a/kernel/auditsc=2Ec b/kernel/auditsc=2Ec >> > index 6f0d6fb6523f=2E=2Ee4ef5e57dde9 100644 >> > --- a/kernel/auditsc=2Ec >> > +++ b/kernel/auditsc=2Ec >> > @@ -2730,7 +2730,7 @@ void __audit_ptrace(struct task_struct *t= ) >> > context->target_uid =3D task_uid(t); >> > context->target_sessionid =3D audit_get_sessionid(t); >> > security_task_getsecid_obj(t, &context->target_sid); >> > - memcpy(context->target_comm, t->comm, TASK_COMM_LEN); >> > + strscpy(context->target_comm, t->comm); >> > } >> > >> > /** >> >> Ahh, the actual generic definition is in =2E >> You could do >> >> diff --git i/include/linux/string=2Eh w/include/linux/string=2E= h >> index 9edace076ddb=2E=2E060504719904 100644 >> --- i/include/linux/string=2Eh >> +++ w/include/linux/string=2Eh >> @@ -76,11 +76,11 @@ ssize_t sized_strscpy(char *, const char *,= size_t); >> * known size=2E >> */ >> #define __strscpy0(dst, src, =2E=2E=2E) \ >> - sized_strscpy(dst, src, sizeof(dst) + __must_be_array(d= st)) >> + sized_strscpy(dst, src, ARRAY_SIZE(dst)) >> #define __strscpy1(dst, src, size) sized_strscpy(dst, src,= size) >> >> #define __strscpy_pad0(dst, src, =2E=2E=2E) \ >> - sized_strscpy_pad(dst, src, sizeof(dst) + __must_be_arr= ay(dst)) >> + sized_strscpy_pad(dst, src, ARRAY_SIZE(dst)) >> #define __strscpy_pad1(dst, src, size) sized_strscpy_pad(dst, = src, size) >> >> /** > >Thank you for your suggestion=2E How does the following commit log look >to you? Does it meet your expectations? > > string: Use ARRAY_SIZE() in strscpy() > > We can use ARRAY_SIZE() instead to clarify that they are regular char= acters=2E > > Co-developed-by: Alejandro Colomar > Signed-off-by: Alejandro Colomar > Signed-off-by: Yafang Shao > >diff --git a/arch/um/include/shared/user=2Eh b/arch/um/include/shared/use= r=2Eh >index bbab79c0c074=2E=2E07216996e3a9 100644 >--- a/arch/um/include/shared/user=2Eh >+++ b/arch/um/include/shared/user=2Eh >@@ -14,7 +14,7 @@ > * copying too much infrastructure for my taste, so userspace files > * get less checking than kernel files=2E > */ >-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) >+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]) + __must_be_array(x)) > > /* This is to get size_t and NULL */ > #ifndef __UM_HOST__ >@@ -60,7 +60,7 @@ static inline void print_hex_dump(const char *level, >const char *prefix_str, > extern int in_aton(char *str); > extern size_t strlcat(char *, const char *, size_t); > extern size_t sized_strscpy(char *, const char *, size_t); >-#define strscpy(dst, src) sized_strscpy(dst, src, sizeof(dst)) >+#define strscpy(dst, src) sized_strscpy(dst, src, ARRAY_SIZE(dst)) Uh, but why? strscpy() copies bytes, not array elements=2E Using sizeof() = is already correct and using ARRAY_SIZE() could lead to unexpectedly small = counts (in admittedly odd situations)=2E What is the problem you're trying to solve here? -Kees --=20 Kees Cook