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 82341C433F5 for ; Tue, 26 Oct 2021 02:24:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51DC460FC2 for ; Tue, 26 Oct 2021 02:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233933AbhJZC04 (ORCPT ); Mon, 25 Oct 2021 22:26:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229998AbhJZC0y (ORCPT ); Mon, 25 Oct 2021 22:26:54 -0400 Received: from mail-io1-xd2d.google.com (mail-io1-xd2d.google.com [IPv6:2607:f8b0:4864:20::d2d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 12123C061745; Mon, 25 Oct 2021 19:24:31 -0700 (PDT) Received: by mail-io1-xd2d.google.com with SMTP id n10so8740705iod.13; Mon, 25 Oct 2021 19:24:31 -0700 (PDT) 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=/GAImBcqzGF4ZlKPfVyKeIteXxvhu81c3zR5LkKqlwY=; b=HckTWrHAKpA9NZaDoBD2BNIf8fBKYacL3yGZ+CmJTO2viT8TEvn6v4CXE5/MtmD3wy eAoYl2oIe7HeG5FcGIaPzaE6CEuiH6ZkKKQ9dLnt7VuKtJeea3Mjpw21tZOjWjlS+8vO zLbZeiwh3xYW6HpdYXoz4CkXS+cf/UMI8DG0JVazxbno27ArXIfeY4GaTnsP1sydjXFr ayX5Ge09SgMHgIoClCs/l+KSLWg0OURLJGKdRC62NTmdIC7Cb+NOI3rNPLrEQsuxg8J5 zCJvRfrF17lPOWTDUF0EgqHPKuoreW6wCp/PfyWozgwykrOfyHraYfRztxnTZEshUVoN HydQ== 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=/GAImBcqzGF4ZlKPfVyKeIteXxvhu81c3zR5LkKqlwY=; b=50ufQ+j4y1mtTzGM01tTtAOmWbjQk2AeRcBgelhcRDjrU6jWYmmfsDA/svyg1xNidQ EqEgYQPkAyCtwaGvMv6uH4BIVlX/PiiLx6OB/ujUNb58JbOvwnAdNwboi0jaLfEoq1JX DRplhUeJTDocL5M6nhle4dci0+XgsILVFtC3cbcxXOR4Bm0mw5mr7as6sjwD7Fr8hEaI Ymv2ilJmzwfTWAkGz5jNdQvbgOP0Mu/Vu8SXhGFutFh2JxmXQbjqLE+jmdN17YrvO7H3 4yGEn4p1Oc92oRKMOTW6pq6dh9/tnE84HO2VrNLKvpP6ZjLv2+Iqxuvf59VIvvvveKQl AmYA== X-Gm-Message-State: AOAM532B5GTYo0JhW/4eSULTgG5Q0xl87MLGBSUhQG90IcjlgZI/9p3j kj5qFUP+w2Vnq8/JCcAXIglZA2nsAk4h1f1vCjs= X-Google-Smtp-Source: ABdhPJxvXEqIO8vqTWxsYX6HC3Vxi6T3FWqsGQ75A1upKsImFHiyikOsYrF3Livq3yt5hVdH592yN3ANmyCD09/8e8c= X-Received: by 2002:a02:a483:: with SMTP id d3mr3945986jam.23.1635215070448; Mon, 25 Oct 2021 19:24:30 -0700 (PDT) MIME-Version: 1.0 References: <20211025083315.4752-1-laoar.shao@gmail.com> <20211025083315.4752-13-laoar.shao@gmail.com> <202110251431.F594652F@keescook> In-Reply-To: <202110251431.F594652F@keescook> From: Yafang Shao Date: Tue, 26 Oct 2021 10:23:54 +0800 Message-ID: Subject: Re: [PATCH v6 12/12] kernel/kthread: show a warning if kthread's comm is truncated To: Kees Cook Cc: Andrew Morton , Steven Rostedt , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Petr Mladek , Peter Zijlstra , Al Viro , Valentin Schneider , Qiang Zhang , robdclark , christian , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Vincent Guittot , David Miller , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin Lau , Song Liu , Yonghong Song , john fastabend , KP Singh , dennis.dalessandro@cornelisnetworks.com, mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com, jgg@ziepe.ca, linux-rdma@vger.kernel.org, netdev , bpf , "linux-perf-use." , linux-fsdevel@vger.kernel.org, Linux MM , LKML , kernel test robot , kbuild test robot , Andrii Nakryiko Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Oct 26, 2021 at 5:35 AM Kees Cook wrote: > > On Mon, Oct 25, 2021 at 08:33:15AM +0000, Yafang Shao wrote: > > Show a warning if task comm is truncated. Below is the result > > of my test case: > > > > truncated kthread comm:I-am-a-kthread-with-lon, pid:14 by 6 characters > > > > Suggested-by: Petr Mladek > > Signed-off-by: Yafang Shao > > Reviewed-by: Kees Cook > > Cc: Mathieu Desnoyers > > Cc: Arnaldo Carvalho de Melo > > Cc: Andrii Nakryiko > > Cc: Peter Zijlstra > > Cc: Steven Rostedt > > Cc: Al Viro > > Cc: Kees Cook > > Cc: Petr Mladek > > --- > > kernel/kthread.c | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/kthread.c b/kernel/kthread.c > > index 5b37a8567168..46b924c92078 100644 > > --- a/kernel/kthread.c > > +++ b/kernel/kthread.c > > @@ -399,12 +399,17 @@ struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data), > > if (!IS_ERR(task)) { > > static const struct sched_param param = { .sched_priority = 0 }; > > char name[TASK_COMM_LEN]; > > + int len; > > > > /* > > * task is already visible to other tasks, so updating > > * COMM must be protected. > > */ > > - vsnprintf(name, sizeof(name), namefmt, args); > > + len = vsnprintf(name, sizeof(name), namefmt, args); > > + if (len >= TASK_COMM_LEN) { > > And since this failure case is slow-path, we could improve the warning > as other had kind of suggested earlier with something like this instead: > It Makes sense to me. I will do it as you suggested. > char *full_comm; > > full_comm = kvasprintf(GFP_KERNEL, namefmt, args); > pr_warn("truncated kthread comm '%s' to '%s' (pid:%d)\n", > full_comm, name); > > kfree(full_comm); > } > > set_task_comm(task, name); > > /* > > * root may have changed our (kthreadd's) priority or CPU mask. > > -- > > 2.17.1 > > > > -- > Kees Cook -- Thanks Yafang