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 61D1AC4332F for ; Fri, 12 Nov 2021 01:05:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A79C6112E for ; Fri, 12 Nov 2021 01:05:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234652AbhKLBIA (ORCPT ); Thu, 11 Nov 2021 20:08:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59044 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234625AbhKLBH7 (ORCPT ); Thu, 11 Nov 2021 20:07:59 -0500 Received: from mail-qt1-x833.google.com (mail-qt1-x833.google.com [IPv6:2607:f8b0:4864:20::833]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD68EC061766; Thu, 11 Nov 2021 17:05:08 -0800 (PST) Received: by mail-qt1-x833.google.com with SMTP id f20so6734304qtb.4; Thu, 11 Nov 2021 17:05:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=fXIzR4H7rC51zoCliJSnruG3gN++VRKIsy1ed6L1uZ0=; b=nahxv2cN/OPoduTjxYuNz1wjlJTPzrf+j7EJDi5o315fzmzSXE3lk519tlit7AgmLM 5L+QlE/H1xO1r/kc91HECc3YRKpLyqx09c7oT9vn30n1jm02RW0i3xGEO5eWeGgHlfW9 6VSQdjPR377+WUR0sMdg1l0I2yKNEPUpBdOBKXM5mRfUXpdGzfVLFuZ8Nv7DupTynkIe BF7YIEyZd9xN4RyU/T0a3pssM65Mm0RFjAE9wPHqBCGDh6n7uCw3hnU/o5XV5q3vJC1G vMmIqWVH0lig3JTV3iJQ1yYRpvRc5WjWSA+7kXGzvVrDnaxWW2oMoBUcVnDn4yJM/VhM xcNA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=fXIzR4H7rC51zoCliJSnruG3gN++VRKIsy1ed6L1uZ0=; b=6B8d6Ei8jxsqv10zFU9gU2qrAo3kkRdQvMW0bhmqMAQ3ahS6oICodG0FJPv1N0cGbs sVF9dysQxX6qnkmnGfZJD9Yhg1kOtCrdVyGH48XICrq6CMxQ7tvRXW/AOj/bUyFCnRBU RE0LCTm6h9h9Ey3q2+m7J2saxq1ByzkPXIjXH5c0ZslXaefLTeRhp94xhmrCMawy9yHm RIbPEeYDm5Y14+pHqmBRbTH52Aw7D3XeKteofNnqIwlblXVzNB2BT23C8qfIRK1lnuic oSxqzHN+6sq4/xNC2CkFHKP3CHt2R8vL0gdCaiSIpOCZ1t9lp5wRHLohDv8gYJM+9KMd hjRA== X-Gm-Message-State: AOAM531IC256vqhIsoTOsN434vApuy6p7sSEbAcnbKQLZjZqZNDz69++ mU8NL3rw4sGhdGJK1JcLMd+doIwAUb0b9J49V7M= X-Google-Smtp-Source: ABdhPJyI15v6hfbPLVFglCWNTP1c+ur2pT58CD6zvbF3WVkubZRvuIGJW+6csH/fYOnC6Xy11GFkA/YMw9b/TRBReIw= X-Received: by 2002:a05:622a:194:: with SMTP id s20mr12323495qtw.66.1636679107925; Thu, 11 Nov 2021 17:05:07 -0800 (PST) MIME-Version: 1.0 References: <20211108083840.4627-1-laoar.shao@gmail.com> <20211108083840.4627-5-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Fri, 12 Nov 2021 09:03:40 +0800 Message-ID: Subject: Re: [PATCH 4/7] fs/binfmt_elf: use get_task_comm instead of open-coded string copy To: Petr Mladek Cc: David Hildenbrand , Andrew Morton , netdev , bpf , "linux-perf-use." , linux-fsdevel@vger.kernel.org, Linux MM , LKML , kernel test robot , kbuild test robot , Kees Cook , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Andrii Nakryiko , Michal Miroslaw , Peter Zijlstra , Steven Rostedt , Matthew Wilcox , Al Viro Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Nov 11, 2021 at 7:35 PM Petr Mladek wrote: > > 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. > I think we can just add some comments to make it grepable, for example, + /* TASK_COMM_LEN */ char pr_fname[16]; or a more detailed explanation: + /* + * The hard-coded 16 is derived from TASK_COMM_LEN, but it can be changed as + * it is exposed to userspace. We'd better make it hard-coded here. + */ char pr_fname[16]; -- Thanks Yafang