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 X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_RED,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49778C433DB for ; Mon, 15 Mar 2021 06:58:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BA98964E40 for ; Mon, 15 Mar 2021 06:58:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA98964E40 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2C5626B0006; Mon, 15 Mar 2021 02:58:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2731F6B006C; Mon, 15 Mar 2021 02:58:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 116FC6B0070; Mon, 15 Mar 2021 02:58:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0116.hostedemail.com [216.40.44.116]) by kanga.kvack.org (Postfix) with ESMTP id EB7406B0006 for ; Mon, 15 Mar 2021 02:58:56 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B08D58249980 for ; Mon, 15 Mar 2021 06:58:56 +0000 (UTC) X-FDA: 77921206272.01.616396B Received: from mail-qt1-f178.google.com (mail-qt1-f178.google.com [209.85.160.178]) by imf13.hostedemail.com (Postfix) with ESMTP id 30989E0011ED for ; Mon, 15 Mar 2021 06:58:56 +0000 (UTC) Received: by mail-qt1-f178.google.com with SMTP id u7so8398503qtq.12 for ; Sun, 14 Mar 2021 23:58:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=IU5V4mabE/n2VCRh3kSmfdhuEAACW74e/YNmNcSi3W8=; b=QdhmEyhcxyXwVDR8NjUH/7ppDoyROqwTDE670AXXQmtFChEdYuZki5fhCpd6P68hxZ Y21sjoK48mK/a62E28b9/N+oxL/IEol2w/iP1zkhiAdn4neTjw73fwdorPEw5nYIcTM9 zGD0rVhMCXMIVVfIgUGJmliNYgomQ4uJVgZlLpvGiHumU2YbVPgMeONAzOcg0IXcfM+K e8XrSRfdRxTRdGgP5J+jYYWn5FhDqA5RBQbqLLymakk+zSwGoixcNubo3YIP1GwbdVzO ieLO4B1Dl7xRtri8oGKJz0PqFAhMkm6FB6sex6h/t1EESM4HYClp59EF09NSorHVK12H jNHQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=IU5V4mabE/n2VCRh3kSmfdhuEAACW74e/YNmNcSi3W8=; b=egDM+aujUVA2M3tiB/tzi4LyF5JvLxkxX77D1D5BidphWtAc2RmWPCxhWhA3ZhQP3g FfXqYgdy1rdK2ILHl1oVkrz0Z2RPy5V+91iCRtHUTJ6B+M/7njAJOr4A+zjk3fbt6y26 HHkVJ9MMX48YtjlKRPYsUTixHc1JWY+0gDpeH6I5WfMz1Q1j6bO1Qb+w1kpoAtMONfLE 8nkZ/4V3V+EVTF9ZHDzTo2hbkH9Ux/ClAW5tGL0nnyrr++r+tERjPrNjENumHoJ75sVE JvcefYdIOjd3qO1IV99VkfbH/QXSBfJWs+Glg0EWsPan3abMQlyhgoB5bP4qtc4mvDWB Vw3Q== X-Gm-Message-State: AOAM530ykWM4ucCFSN+4qAIjYTyUD6mYskbBw53851ntp+Y+aHECs+Cu KynuMnS4tRUgfqQKEeKvf4WvXI9ADRPL8o3GvIUOyw== X-Google-Smtp-Source: ABdhPJw1nDPMaGuD+I/Gyg5vA/5WTioXa+s8ugiYlPtLXZ1fT5Oc3wV3ImBGwIyFbtBVjuIobFZYNfiGA87XfCiM7TY= X-Received: by 2002:ac8:7318:: with SMTP id x24mr21525417qto.67.1615791535245; Sun, 14 Mar 2021 23:58:55 -0700 (PDT) MIME-Version: 1.0 References: <20210315015940.11788-1-walter-zh.wu@mediatek.com> In-Reply-To: <20210315015940.11788-1-walter-zh.wu@mediatek.com> From: Dmitry Vyukov Date: Mon, 15 Mar 2021 07:58:44 +0100 Message-ID: Subject: Re: [PATCH] task_work: kasan: record task_work_add() call stack To: Walter Wu Cc: Andrey Ryabinin , Alexander Potapenko , Matthias Brugger , Andrey Konovalov , Andrew Morton , Jens Axboe , Oleg Nesterov , kasan-dev , Linux-MM , LKML , Linux ARM , wsd_upstream , linux-mediatek@lists.infradead.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 30989E0011ED X-Stat-Signature: synfbm4zt4o6zfhaufttrx1euuhqknmk Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf13; identity=mailfrom; envelope-from=""; helo=mail-qt1-f178.google.com; client-ip=209.85.160.178 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615791536-504537 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 Mon, Mar 15, 2021 at 3:00 AM Walter Wu wrote: > > Why record task_work_add() call stack? > Syzbot reports many use-after-free issues for task_work, see [1]. > After see the free stack and the current auxiliary stack, we think > they are useless, we don't know where register the work, this work > may be the free call stack, so that we miss the root cause and > don't solve the use-after-free. > > Add task_work_add() call stack into KASAN auxiliary stack in > order to improve KASAN report. It is useful for programmers > to solve use-after-free issues. > > [1]: https://groups.google.com/g/syzkaller-bugs/search?q=kasan%20use-after-free%20task_work_run > > Signed-off-by: Walter Wu > Suggested-by: Dmitry Vyukov > Cc: Andrey Ryabinin > Cc: Dmitry Vyukov > Cc: Andrey Konovalov > Cc: Alexander Potapenko > Cc: Andrew Morton > Cc: Matthias Brugger > Cc: Jens Axboe > Cc: Oleg Nesterov > --- > kernel/task_work.c | 3 +++ > mm/kasan/kasan.h | 2 +- > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/kernel/task_work.c b/kernel/task_work.c > index 9cde961875c0..f255294377da 100644 > --- a/kernel/task_work.c > +++ b/kernel/task_work.c > @@ -55,6 +55,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work, > break; > } > > + /* record the work call stack in order to print it in KASAN reports */ > + kasan_record_aux_stack(work); I think this call should be done _before_ we actually queue the work, because this function may operate on non-current task. Consider, we queue the work, the other task already executes it and triggers use-after-free, now only now we record the stack. Moreover, I think we can trigger use-after-free here ourselves while recording the aux stack. We queued the work, and the work can cause own free, so it's not necessary live by now. > return 0; > } > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > index 3436c6bf7c0c..d300fe9415bd 100644 > --- a/mm/kasan/kasan.h > +++ b/mm/kasan/kasan.h > @@ -146,7 +146,7 @@ struct kasan_alloc_meta { > struct kasan_track alloc_track; > #ifdef CONFIG_KASAN_GENERIC > /* > - * call_rcu() call stack is stored into struct kasan_alloc_meta. > + * Auxiliary stack is stored into struct kasan_alloc_meta. > * The free stack is stored into struct kasan_free_meta. > */ > depot_stack_handle_t aux_stack[2]; > -- > 2.18.0