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Mon, 25 Oct 2021 22:24:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0178.hostedemail.com [216.40.44.178]) by kanga.kvack.org (Postfix) with ESMTP id A904B940007 for ; Mon, 25 Oct 2021 22:24:31 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 5BB9B1809CD75 for ; Tue, 26 Oct 2021 02:24:31 +0000 (UTC) X-FDA: 78736994742.25.4B21AE7 Received: from mail-io1-f47.google.com (mail-io1-f47.google.com [209.85.166.47]) by imf21.hostedemail.com (Postfix) with ESMTP id 337E6D042B65 for ; Tue, 26 Oct 2021 02:24:28 +0000 (UTC) Received: by mail-io1-f47.google.com with SMTP id 188so18144890iou.12 for ; Mon, 25 Oct 2021 19:24:30 -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=sfcr34GgkRNVs75duw8j1zmis4JrHZ1r36czNMd7HONUOUmQsrxW6wSb0kJirhs2kF VjGrywf23SPNltCokLkdV4CilGro63PvrTPRMo3dwMzeLSybehU7G/P+sDnID9Ux+a4r iifgFQs/3tkB+7S8U5+9UNshpRXUjZlVhuBWGqT+WNMN1UOENG50646NIcJ/q8ytHYh4 4NHBZZPPCV8DdBkgzLnpkm9QzXf6xC6EttdVAvkxdyv1sLWiyztao1wSYYgxYNWPfKm0 5tERlNGnbOxj0yys6mBH64STZMw/9awDqoG6AOed9txkgdD33Og/fflFz2jnC7WBnhYS xzxw== X-Gm-Message-State: AOAM532lAfbc+jY11fUILNqmfBrPE41HIeq9r5w/hs3PE0xE/M7bmcqd d6v3cmRJn5XS9tsRnbUAlm9ge01bI9kv3tYXwc0= 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" X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 337E6D042B65 X-Stat-Signature: irqtmken5fuq91ypeid1zbpzb6354kec Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=HckTWrHA; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf21.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.166.47 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com X-HE-Tag: 1635215068-821137 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 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