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_BLOCKED,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 21DFDC4320E for ; Mon, 30 Aug 2021 05:45:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DDC8A60F92 for ; Mon, 30 Aug 2021 05:45:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231844AbhH3FmP (ORCPT ); Mon, 30 Aug 2021 01:42:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39922 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229936AbhH3FmM (ORCPT ); Mon, 30 Aug 2021 01:42:12 -0400 Received: from mail-ot1-x32f.google.com (mail-ot1-x32f.google.com [IPv6:2607:f8b0:4864:20::32f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78F19C061575 for ; Sun, 29 Aug 2021 22:41:19 -0700 (PDT) Received: by mail-ot1-x32f.google.com with SMTP id o16-20020a9d2210000000b0051b1e56c98fso16981230ota.8 for ; Sun, 29 Aug 2021 22:41:19 -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=uXQwyCT+Qsc8uZwkoBR6K3wOBnEuFGSecqZVp4Xa4gk=; b=wSqv63ctLC9ur2QzK3Ocbr+w93SUqKkVwPSpCLMxiHLTH9WYnWC3q0ljXwYn44NfEn wRFg7b0tq+/1zfIJhUqFh+ydqiQVbIeZccI2X5oiVJDLV1bWYlYawOdXgPI9koRkZSD9 Sf+yjNsrjgJheoIWEcG9/iYZtuhmSiAcCoZEVvM3sgUIPD6+je1LkSv9KMGqGnQz0msH h1SxOwA+YoJNo8ei4GL7G7cZ6WGZNVlfca7b4HFGkzhlg+nCn18tP6H/HgNPbIKETvAD Zr9lJayaUWkNPGGRJs2/PXVY9IV+gQVFM3iVd9MWWnDzd+J9prPO9xTmo4FG5zoniULh UzAA== 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=uXQwyCT+Qsc8uZwkoBR6K3wOBnEuFGSecqZVp4Xa4gk=; b=V2QV4Y16b3uem9ZD5fki0AJZkaMrDfOtbyqCk6fAD2kLyD/BemolwRuWUSz/pCWgoN JrmNwBuuAFRJmSosKtmPLv/DX2iRdJWM1pA11go+6W5Io2AsZFSYODppNd5bz+NH9h0P oQLR77s/uXcsWoaXLfW3WPQigRjcsTBJl1DBzlWpAlZ8aVzJRUymE1tkhR9IuGu93AI9 HPuvj78A68oTC8BkYfY+MtuJ1nhgGSMuEZ/p7bI2XsFQIyGS3lO8H3s7dBV91mKJXwzi 9xPIUcobWvLcxW64xT2i9oW9FIiyNeYxY/WiK8AlaEHxRgIlUHwHVvm1nRglRS/5NL3g cWPA== X-Gm-Message-State: AOAM533C0rlrk4Ibm0iSLGZGJcXJRpH37nIvH2ep6FQzaGBMDDLzNeT1 nMfCuE6H5Ahku2PXXWk8/zo05kDsRP9g6slZ31KCFQ== X-Google-Smtp-Source: ABdhPJzxU2Ioy5wBqpud0WTdoo3mnvx31y5RcePZXQuX27lgpP0t3JH0Us/BlgQZdUrzYpNTeDHictwTzHnCrNXRql0= X-Received: by 2002:a05:6830:2363:: with SMTP id r3mr18756962oth.148.1630302078278; Sun, 29 Aug 2021 22:41:18 -0700 (PDT) MIME-Version: 1.0 References: <20210827234910.40490-1-skhan@linuxfoundation.org> In-Reply-To: <20210827234910.40490-1-skhan@linuxfoundation.org> From: Dmitry Vyukov Date: Mon, 30 Aug 2021 07:40:00 +0200 Message-ID: Subject: Re: [PATCH] workqueue: Don't record workqueue stack holding raw_spin_lock To: Shuah Khan Cc: tj@kernel.org, jiangshanlai@gmail.com, elver@google.com, akpm@linux-foundation.org, walter-zh.wu@mediatek.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 28 Aug 2021 at 01:49, Shuah Khan wrote: > > When CONFIG_PROVE_RAW_LOCK_NESTING and CONFIG_KASAN are enabled, > kasan_record_aux_stack() runs into "BUG: Invalid wait context" when > it tries to allocate memory attempting to acquire spinlock in page > allocation code while holding workqueue pool raw_spinlock. > > There are several instances of this problem when block layer tries > to __queue_work(). Call trace from one of these instances is below: > > kblockd_mod_delayed_work_on() > mod_delayed_work_on() > __queue_delayed_work() > __queue_work() (rcu_read_lock, raw_spin_lock pool->lock held) > insert_work() > kasan_record_aux_stack() > kasan_save_stack() > stack_depot_save() > alloc_pages() > __alloc_pages() > get_page_from_freelist() > rm_queue() > rm_queue_pcplist() > local_lock_irqsave(&pagesets.lock, flags); > [ BUG: Invalid wait context triggered ] > > Fix it by calling kasan_record_aux_stack() without holding pool lock. > There is no need to hold pool lock in this path. > > ============================= > [ BUG: Invalid wait context ] > 5.14.0-rc7+ #8 Not tainted > ----------------------------- > snap/532 is trying to lock: > ffff888374f32ba0 (lock#2){..-.}-{3:3}, at: get_page_from_freelist (mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165) > other info that might help us debug this: > context-{5:5} > 3 locks held by snap/532: > #0: ffff888139fa4408 (&type->i_mutex_dir_key#10){.+.+}-{4:4}, at: walk_component (fs/namei.c:1663 fs/namei.c:1959) > #1: ffffffffab870c40 (rcu_read_lock){....}-{1:3}, at: __queue_work (./arch/x86/include/asm/preempt.h:80 ./include/linux/rcupdate.h:68 ./include/linux/rcupdate.h:685 kernel/workqueue.c:1421) > #2: ffff888374f36cd8 (&pool->lock){-.-.}-{2:2}, at: __queue_work (kernel/workqueue.c:1466) > stack backtrace: > CPU: 14 PID: 532 Comm: snap Not tainted 5.14.0-rc7+ #8 > Hardware name: LENOVO 90Q30008US/3728, BIOS O4ZKT1CA 09/16/2020 > Call Trace: > dump_stack_lvl (lib/dump_stack.c:106 (discriminator 4)) > dump_stack (lib/dump_stack.c:113) > __lock_acquire.cold (kernel/locking/lockdep.c:4666 kernel/locking/lockdep.c:4727 kernel/locking/lockdep.c:4965) > ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4873) > ? lock_is_held_type (kernel/locking/lockdep.c:5368 kernel/locking/lockdep.c:5668) > lock_acquire (kernel/locking/lockdep.c:438 kernel/locking/lockdep.c:5627 kernel/locking/lockdep.c:5590) > ? get_page_from_freelist (mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165) > ? lock_release (kernel/locking/lockdep.c:5593) > ? __kasan_check_read (mm/kasan/shadow.c:32) > ? __lock_acquire (kernel/locking/lockdep.c:5019) > ? __zone_watermark_ok (./include/linux/list.h:282 ./include/linux/mmzone.h:111 mm/page_alloc.c:3908) > get_page_from_freelist (./include/linux/local_lock_internal.h:43 mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165) > ? get_page_from_freelist (mm/page_alloc.c:3665 mm/page_alloc.c:3703 mm/page_alloc.c:4165) > ? lock_is_held_type (kernel/locking/lockdep.c:5368 kernel/locking/lockdep.c:5668) > ? is_bpf_text_address (./arch/x86/include/asm/preempt.h:85 ./include/linux/rcupdate.h:73 ./include/linux/rcupdate.h:719 kernel/bpf/core.c:708) > ? lock_downgrade (kernel/locking/lockdep.c:5633) > ? __zone_watermark_ok (mm/page_alloc.c:4054) > __alloc_pages (mm/page_alloc.c:5391) > ? __alloc_pages_slowpath.constprop.0 (mm/page_alloc.c:5354) > ? create_prof_cpu_mask (kernel/stacktrace.c:82) > ? _find_first_bit (lib/find_bit.c:83) > alloc_pages (mm/mempolicy.c:2249) > stack_depot_save (lib/stackdepot.c:304) > ? lock_is_held_type (kernel/locking/lockdep.c:5368 kernel/locking/lockdep.c:5668) > kasan_save_stack (mm/kasan/common.c:41) > ? kasan_save_stack (mm/kasan/common.c:39) > ? kasan_record_aux_stack (mm/kasan/generic.c:348) > ? insert_work (./include/linux/instrumented.h:71 ./include/asm-generic/bitops/instrumented-non-atomic.h:134 kernel/workqueue.c:616 kernel/workqueue.c:623 kernel/workqueue.c:1335) > ? __queue_work (kernel/workqueue.c:1501) > ? __queue_delayed_work (kernel/workqueue.c:1657) > ? mod_delayed_work_on (kernel/workqueue.c:1720) > ? kblockd_mod_delayed_work_on (block/blk-core.c:1633) > ? __blk_mq_delay_run_hw_queue (block/blk-mq.c:1567) > ? blk_mq_run_hw_queue (block/blk-mq.c:1610) > ? blk_mq_sched_insert_request (block/blk-mq-sched.c:480) > ? blk_mq_submit_bio (block/blk-mq.c:2276) > > Fixes: e89a85d63fb2 ("workqueue: kasan: record workqueue stack") > Signed-off-by: Shuah Khan > --- > kernel/workqueue.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index f148eacda55a..e647b29b9fb0 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -1328,9 +1328,6 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work, > { > struct worker_pool *pool = pwq->pool; > > - /* record the work call stack in order to print it in KASAN reports */ > - kasan_record_aux_stack(work); > - > /* we own @work, set data and link */ > set_work_pwq(work, pwq, extra_flags); > list_add_tail(&work->entry, head); > @@ -1499,6 +1496,14 @@ static void __queue_work(int cpu, struct workqueue_struct *wq, > > out: > raw_spin_unlock(&pwq->pool->lock); > + > + /* > + * record the work call stack in order to print it in KASAN reports > + * Do this without pool raw_spinlock hold to avoid nesting raw > + * spinlock with page allocation spinlock. > + */ > + kasan_record_aux_stack(work); Hi Shuah, I agree that the current code is problematic and we don't need to hold the lock around kasan_record_aux_stack(). However, I think we need to call kasan_record_aux_stack() before the actual queueing, otherwise the work can be dequeued and cause a bug before we call kasan_record_aux_stack() in this task (it's like setting permissions on an fd after publishing it in fd table). Also, this happens after "out:" label and it seems we go to it even if we don't queue the work in some cases. Ideally we only call kasan_record_aux_stack() only if we queue it, because the capacity for aux stacks are only 2 stacks (the oldest gets evicted). However, I think the first point is more important. So if move kasan_record_aux_stack() to happen before insert_work() and won't be able to predict if we actually queue it later or not, then I think it's fine to episodically call kasan_record_aux_stack() even if we don't queue later. At least I don't see a better solution. > rcu_read_unlock(); > } > > @@ -3012,6 +3017,13 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, > insert_wq_barrier(pwq, barr, work, worker); > raw_spin_unlock_irq(&pool->lock); > > + /* > + * record the work call stack in order to print it in KASAN reports > + * Do this without pool raw_spinlock hold to avoid nesting raw > + * spinlock with page allocation spinlock. > + */ > + kasan_record_aux_stack(work); > + > /* > * Force a lock recursion deadlock when using flush_work() inside a > * single-threaded or rescuer equipped workqueue. > -- > 2.30.2 >