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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8B8BC433F5 for ; Thu, 11 Nov 2021 11:35:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9182961208 for ; Thu, 11 Nov 2021 11:35:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9182961208 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 060A16B0087; Thu, 11 Nov 2021 06:35:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 011876B0088; Thu, 11 Nov 2021 06:35:03 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E41CB6B0089; Thu, 11 Nov 2021 06:35:03 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0032.hostedemail.com [216.40.44.32]) by kanga.kvack.org (Postfix) with ESMTP id D66476B0087 for ; Thu, 11 Nov 2021 06:35:03 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9889418499AC2 for ; Thu, 11 Nov 2021 11:35:03 +0000 (UTC) X-FDA: 78796442886.24.C08DE51 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf05.hostedemail.com (Postfix) with ESMTP id 6BCA35090857 for ; Thu, 11 Nov 2021 11:34:41 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 8CAEA21B35; Thu, 11 Nov 2021 11:35:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1636630501; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JF8tqJ/qYg7iprU4Smn80buBhFNtzpmt6OjhcdUzme4=; b=tQs9jwdvsxjCgUy1YjhWC29W8ruybAG4J6MEmsTVUl02QFHxRH/s1s/9OHEiuUPFVici7l a7IIKOvAHN0uhNPRfQ9w31C41z0iH87gt/kcggUdS4rbeZX90inzrYufC8X4JKmsrqAU/J 8qSJkb29gfd827eZ2067ocolEPYIeIc= Received: from suse.cz (unknown [10.100.216.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id D0F91A3B83; Thu, 11 Nov 2021 11:35:00 +0000 (UTC) Date: Thu, 11 Nov 2021 12:34:57 +0100 From: Petr Mladek To: David Hildenbrand Cc: Yafang Shao , akpm@linux-foundation.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, oliver.sang@intel.com, lkp@intel.com, Kees Cook , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Andrii Nakryiko , Michal Miroslaw , Peter Zijlstra , Steven Rostedt , Matthew Wilcox , Al Viro Subject: Re: [PATCH 4/7] fs/binfmt_elf: use get_task_comm instead of open-coded string copy Message-ID: References: <20211108083840.4627-1-laoar.shao@gmail.com> <20211108083840.4627-5-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6BCA35090857 X-Stat-Signature: zsbqjxprdicf9ids6sc3jgshsas984wi Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=tQs9jwdv; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf05.hostedemail.com: domain of pmladek@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=pmladek@suse.com X-HE-Tag: 1636630481-112608 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: On Thu 2021-11-11 11:06:04, David Hildenbrand wrote: > On 11.11.21 11:03, David Hildenbrand wrote: > > On 08.11.21 09:38, Yafang Shao wrote: > >> It is better to use get_task_comm() instead of the open coded string > >> copy as we do in other places. > >> > >> struct elf_prpsinfo is used to dump the task information in userspace > >> coredump or kernel vmcore. Below is the verfication of vmcore, > >> > >> crash> ps > >> PID PPID CPU TASK ST %MEM VSZ RSS COMM > >> 0 0 0 ffffffff9d21a940 RU 0.0 0 0 [swapper/0] > >>> 0 0 1 ffffa09e40f85e80 RU 0.0 0 0 [swapper/1] > >>> 0 0 2 ffffa09e40f81f80 RU 0.0 0 0 [swapper/2] > >>> 0 0 3 ffffa09e40f83f00 RU 0.0 0 0 [swapper/3] > >>> 0 0 4 ffffa09e40f80000 RU 0.0 0 0 [swapper/4] > >>> 0 0 5 ffffa09e40f89f80 RU 0.0 0 0 [swapper/5] > >> 0 0 6 ffffa09e40f8bf00 RU 0.0 0 0 [swapper/6] > >>> 0 0 7 ffffa09e40f88000 RU 0.0 0 0 [swapper/7] > >>> 0 0 8 ffffa09e40f8de80 RU 0.0 0 0 [swapper/8] > >>> 0 0 9 ffffa09e40f95e80 RU 0.0 0 0 [swapper/9] > >>> 0 0 10 ffffa09e40f91f80 RU 0.0 0 0 [swapper/10] > >>> 0 0 11 ffffa09e40f93f00 RU 0.0 0 0 [swapper/11] > >>> 0 0 12 ffffa09e40f90000 RU 0.0 0 0 [swapper/12] > >>> 0 0 13 ffffa09e40f9bf00 RU 0.0 0 0 [swapper/13] > >>> 0 0 14 ffffa09e40f98000 RU 0.0 0 0 [swapper/14] > >>> 0 0 15 ffffa09e40f9de80 RU 0.0 0 0 [swapper/15] > >> > >> It works well as expected. > >> > >> Suggested-by: Kees Cook > >> Signed-off-by: Yafang Shao > >> Cc: Mathieu Desnoyers > >> Cc: Arnaldo Carvalho de Melo > >> Cc: Andrii Nakryiko > >> Cc: Michal Miroslaw > >> Cc: Peter Zijlstra > >> Cc: Steven Rostedt > >> Cc: Matthew Wilcox > >> Cc: David Hildenbrand > >> Cc: Al Viro > >> Cc: Kees Cook > >> Cc: Petr Mladek > >> --- > >> fs/binfmt_elf.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > >> index a813b70f594e..138956fd4a88 100644 > >> --- a/fs/binfmt_elf.c > >> +++ b/fs/binfmt_elf.c > >> @@ -1572,7 +1572,7 @@ static int fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p, > >> SET_UID(psinfo->pr_uid, from_kuid_munged(cred->user_ns, cred->uid)); > >> SET_GID(psinfo->pr_gid, from_kgid_munged(cred->user_ns, cred->gid)); > >> rcu_read_unlock(); > >> - strncpy(psinfo->pr_fname, p->comm, sizeof(psinfo->pr_fname)); > >> + get_task_comm(psinfo->pr_fname, p); > >> > >> return 0; > >> } > >> > > > > We have a hard-coded "pr_fname[16]" as well, not sure if we want to > > adjust that to use TASK_COMM_LEN? > > But if the intention is to chance TASK_COMM_LEN later, we might want to > keep that unchanged. It seems that len will not change in the end. Another solution is going to be used for the long names, see https://lore.kernel.org/r/20211108084142.4692-1-laoar.shao@gmail.com. > (replacing the 16 by a define might still be a good idea, similar to how > it's done for ELF_PRARGSZ, but just a thought) If the code would need some tweaking when the size changes, you could still use TASK_COMM_LEN and trigger a compilation error when the size gets modified. For example, static_assert(TASK_COMM_LEN == 16); It will make it clear that it needs attention if the size is ever modified. Best Regards, Petr