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 210A4C54FAA for ; Wed, 28 Aug 2024 12:58:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9EDFF6B0089; Wed, 28 Aug 2024 08:58:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 99D446B008A; Wed, 28 Aug 2024 08:58:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8650D6B008C; Wed, 28 Aug 2024 08:58:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 690636B0089 for ; Wed, 28 Aug 2024 08:58:26 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 124A3C1EDC for ; Wed, 28 Aug 2024 12:58:26 +0000 (UTC) X-FDA: 82501657812.22.C3B9F20 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf25.hostedemail.com (Postfix) with ESMTP id 45B7CA0008 for ; Wed, 28 Aug 2024 12:58:23 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=INcijHKd; spf=pass (imf25.hostedemail.com: domain of alx@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=alx@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=1724849786; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=/AkLzBe+/Lze/6ijifzo44k6iY9Z1tCZNM5E1tSVzUY=; b=kYMnLvFy/OUkq2KVcL7hQ0X9EnBRMnXSFpRyqBq53wt2tmZm+xGPsYc6UH95HN3+kBCCPO dhSAraWttUrq4/oX+a0eAnU80gDi/qC6fDFuLPdY+iegw2k6tXKWES5XMt3YKedwmrrD0v 2dqug2BnM1kuO2XfquITWVpmN8bqI34= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=INcijHKd; spf=pass (imf25.hostedemail.com: domain of alx@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=alx@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724849786; a=rsa-sha256; cv=none; b=Agn2fHi7ANs4vQxFCHwqJedcXNKjc1vQnFVOfuG3OOyX7H6/KTt2yTwlB2mpDSiANoIZqB JtthZWdpPrGHFn/rcTQQd6yS0jLQVVzj3Z/aZfzquBjaYYiGez5I1vMQYp5qUaKOv20Tpp Z9qnANFA6mCkkdBoqPRwt5BeZnPwkCk= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 73B71A402E1; Wed, 28 Aug 2024 12:58:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ECCEAC98EDF; Wed, 28 Aug 2024 12:58:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724849902; bh=n86jAMr/f3BgwZu+naWFNgdxfrENfR6IstOBFoINw5U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=INcijHKdxjgi3vpAx+1+S/ILXebjKI5bADpOfOi4NopNEYIvGCKxL8t1TBOkImOEH +Z2c2/YU+d5Gaoot+ZNRqHXS9O/KOZkFTKJX0+SJkNYeOXPYY8yVOdVIETooYyKduL qQNBPAQwE0t87a5YZwOjIJx/7vJ4J1gcsO0D+sZGdVeq43YiSf0uH+90AR1t/ZJ0IJ 2w3HaXZLAUqTqiUVE1c6mYTcy/exa0OpW9vw83OcftKX9A1k1GJ2kcLiTXPcjC99E6 kapylEkZBO2AAQAjTgt43Gq2Bpxs/TVo6lj5R2sQjIU49yDy+vkjHQHShrLDcw3EuU QmfxYS2161jHQ== Date: Wed, 28 Aug 2024 14:58:15 +0200 From: Alejandro Colomar To: Yafang Shao 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() Message-ID: References: <20240828030321.20688-1-laoar.shao@gmail.com> <20240828030321.20688-2-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="jlsfvt4o727tdvtw" Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 45B7CA0008 X-Stat-Signature: gk5difsp4ku1qjkjbg7t7yfksqqe98s7 X-Rspam-User: X-HE-Tag: 1724849903-715558 X-HE-Meta: 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 u9fBsSrj 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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: --jlsfvt4o727tdvtw Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable From: Alejandro Colomar To: Yafang Shao 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() References: <20240828030321.20688-1-laoar.shao@gmail.com> <20240828030321.20688-2-laoar.shao@gmail.com> MIME-Version: 1.0 In-Reply-To: On Wed, Aug 28, 2024 at 12:15:40PM GMT, Alejandro Colomar wrote: > Hi Yafang, >=20 > 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: > >=20 > > - The task_lock() is unnecessary > > Quoted from Linus [0]: > > : Since user space can randomly change their names anyway, using lock= ing > > : was always wrong for readers (for writers it probably does make sen= se > > : 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 > >=20 > > - The BUILD_BUG_ON() doesn't add any value > > The only requirement is to ensure that the destination buffer is a va= lid > > array. > >=20 > > - Zeroing is not necessary in current use cases > > To avoid confusion, we should remove it. Moreover, not zeroing could > > potentially make it easier to uncover bugs. If the caller needs a > > zero-padded task name, it should be explicitly handled at the call si= te. > >=20 > > Suggested-by: Linus Torvalds > > Link: https://lore.kernel.org/all/CAHk-=3DwivfrF0_zvf+oj6=3D=3DSh=3D-np= JooP8chLPEfaFV0oNYTTBA@mail.gmail.com [0] > > Link: https://lore.kernel.org/all/CAHk-=3DwhWtUC-AjmGJveAETKOMeMFSTwKwu= 99v7+b6AyHMmaDFA@mail.gmail.com/ > > Suggested-by: Alejandro Colomar > > Link: https://lore.kernel.org/all/2jxak5v6dfxlpbxhpm3ey7oup4g2lnr3ueurf= bosf5wdo65dk4@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. Hallyn" > > --- > > fs/exec.c | 10 ---------- > > fs/proc/array.c | 2 +- > > include/linux/sched.h | 32 ++++++++++++++++++++++++++------ > > kernel/kthread.c | 2 +- > > 4 files changed, 28 insertions(+), 18 deletions(-) > >=20 >=20 > [...] >=20 > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > index f8d150343d42..c40b95a79d80 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h >=20 > [...] >=20 > > @@ -1914,10 +1917,27 @@ static inline void set_task_comm(struct task_st= ruct *tsk, const char *from) > > __set_task_comm(tsk, from, false); > > } > > =20 > > -extern char *__get_task_comm(char *to, size_t len, struct task_struct = *tsk); > > +/* >=20 > [...] >=20 > > + * - ARRAY_SIZE() can help ensure that @buf is indeed an array. > > + */ > > #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)); \ >=20 > I see that there's a two-argument macro >=20 > #define strscpy(dst, src) sized_strscpy(dst, src, sizeof(dst)) >=20 > which is used in patch 2/8 >=20 > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > index 6f0d6fb6523f..e4ef5e57dde9 100644 > --- a/kernel/auditsc.c > +++ b/kernel/auditsc.c > @@ -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); > } >=20 > /** Ahh, the actual generic definition is in . You could do diff --git i/include/linux/string.h w/include/linux/string.h index 9edace076ddb..060504719904 100644 --- i/include/linux/string.h +++ w/include/linux/string.h @@ -76,11 +76,11 @@ ssize_t sized_strscpy(char *, const char *, size_t); * known size. */ #define __strscpy0(dst, src, ...) \ - sized_strscpy(dst, src, sizeof(dst) + __must_be_array(dst)) + sized_strscpy(dst, src, ARRAY_SIZE(dst)) #define __strscpy1(dst, src, size) sized_strscpy(dst, src, size) =20 #define __strscpy_pad0(dst, src, ...) \ - sized_strscpy_pad(dst, src, sizeof(dst) + __must_be_array(dst)) + sized_strscpy_pad(dst, src, ARRAY_SIZE(dst)) #define __strscpy_pad1(dst, src, size) sized_strscpy_pad(dst, src, size) =20 /** >=20 > I propose modifying that macro to use ARRAY_SIZE() instead of sizeof(), > and then calling that macro here too. That would not only make sure > that this is an array, but make sure that every call to that macro is an > array. An if there are macros for similar string functions that reduce > the argument with a usual sizeof(), the same thing could be done to > those too. >=20 > Have a lovley day! > Alex >=20 > > + buf; \ > > }) > > =20 > > #ifdef CONFIG_SMP > > diff --git a/kernel/kthread.c b/kernel/kthread.c > > index f7be976ff88a..7d001d033cf9 100644 > > --- a/kernel/kthread.c > > +++ b/kernel/kthread.c > > @@ -101,7 +101,7 @@ void get_kthread_comm(char *buf, size_t buf_size, s= truct task_struct *tsk) > > struct kthread *kthread =3D to_kthread(tsk); > > =20 > > if (!kthread || !kthread->full_name) { > > - __get_task_comm(buf, buf_size, tsk); > > + strscpy(buf, tsk->comm, buf_size); > > return; > > } > > =20 > > --=20 > > 2.43.5 > >=20 >=20 > --=20 > --=20 --jlsfvt4o727tdvtw Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEE6jqH8KTroDDkXfJAnowa+77/2zIFAmbPHuEACgkQnowa+77/ 2zKgBA//eGa/SyzAmBdUjYfc4f7liEeEv+OWUTlM7ld3iAWQPIRtR+Qi4A8etapm 5a92Z1667JrB0rfpZiBDHdROGwzukfPY/V/Ppj5wF1janRjy7jy98Tc1k8QYSSux bzTNagcGoRRrMcOQoXRsHZmb9VlripTPQj36lApImB0GtnipmfEbSiQns1I03A8/ vnnXEGHRT+EIKyE2Q6LNyanJwqsTI7aZyXOS1Xe3bekkRjmL3cM9cploLxALaiIK OFhjtk10ALjug21HhBO6Fufg3b1m8reK+tl5+3WKi+h4Z+OupJhKvf5i0XLVLXto 1Vu+j/lc/VrR7SIQdFcyKYjWM3Igp/BPSjWpGmYNH/fUE1S3RQoYFAyS3Iy5GbkI jy5s29zvCm1fjfN1/u0/35uxmdzFqRAI72FfoZUKG7DRrLdyEXDwgLRJncCCh9fT 3qxl7Px3MAoXUbtps7p0btpRVO7Xhn9D5OUtYo3RUY4Dcpn9ed2ANI/bdZeyg7hs NbTayf3XNnzN1Tbq7+XBv7E66gV89G36kS65kmE5c6HQ7kwf5yDxwoQfrqgjaFYN bwRxokSRWphrNpHN0pGmaBvJTgBFAizWjhtWl8siOQJPixaW/ga1Ql57UbVE7Qkk SdeJkHw1w492JAct0QQsWOqdyYksI9k6qLG/n4zMwwnVemIWtRg= =aSp9 -----END PGP SIGNATURE----- --jlsfvt4o727tdvtw--