From patchwork Wed Jan 5 14:36:33 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 12705503 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0540C433EF for ; Thu, 6 Jan 2022 15:45:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240669AbiAFPpv (ORCPT ); Thu, 6 Jan 2022 10:45:51 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:47270 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240624AbiAFPps (ORCPT ); Thu, 6 Jan 2022 10:45:48 -0500 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id B576F1F3A8; Thu, 6 Jan 2022 15:45:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1641483945; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oeshiqmmWZD73GkSK4+N+GqKNPAYETIzxJpuE6/zef0=; b=1h9Gr/LPNxTD+nbAWYuY1xHYKDzUweSd9jyJXhTx6so4YECU59JdfAOX9xw2D8Na18Fy+N f623BXGHM9n6rI5gBrJ/LhA9ivaMTMh17IP2FGUWGXESyXbFhUsdjUxHaaRz1ifIxWlkgU I6rf71JyB6jyXrtXwV0iGvWk7TpUA8c= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1641483945; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oeshiqmmWZD73GkSK4+N+GqKNPAYETIzxJpuE6/zef0=; b=/qSqzb2g3P3HU8QwdfzOf826zXr9IM9LXUpLnSrbBtUhHfdpmnzGH0F7TWHpywIVAPg+DI lvbQd6iwtBBf6ECQ== Received: from quack3.suse.cz (unknown [10.163.43.118]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 9C81EA3B8A; Thu, 6 Jan 2022 15:45:45 +0000 (UTC) Received: by localhost (Postfix, from userid 1000) id CBFA9A083A; Wed, 5 Jan 2022 15:36:39 +0100 (CET) From: Jan Kara To: Cc: Paolo Valente , Jens Axboe , "yukuai (C)" , Jan Kara , stable@vger.kernel.org Subject: [PATCH 2/5] bfq: Avoid merging queues with different parents Date: Wed, 5 Jan 2022 15:36:33 +0100 Message-Id: <20220105143639.31266-2-jack@suse.cz> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20220105143037.20542-1-jack@suse.cz> References: <20220105143037.20542-1-jack@suse.cz> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2888; h=from:subject; bh=Wo1FkmvrgLnsLoxUN8FFedXWnRxiaMVst9kwBuKTVTg=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBh1azxCr2kJ3pthS1i4guH+kNkcoxQDTHDYlhq+Qn6 JBmDeFCJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCYdWs8QAKCRCcnaoHP2RA2UmGCA CUjIq/XvhxPKEvNHEmv77TbZdLW/4H+NWEz3Ul4Mi7OKUBmSPfDAqXnG2Ga4wD5aSR2LByk5n81ZSO ps9IHFU71GPaV98e2Z1uEKEUe41s3oHUwm/moq2UqWtUseNet57GFFx8gEBVlNrt6RccaAONRSe4HH uW0gjtuZ9Qbew3edY3/zoL274OD10Pm+XyG81JDL8SZqsIVWNfsGOCi40dIWp2ebFoKBdruT1t9ASv LT+wGMn1ELIAqd0jqvm8dV45UaE5mW2ekX9L18jHAQfm5WO9ksPJaPPzgwePgjG4iw/MOTcDfUAc9b Az/RmgNatgvvYCIlG7YZ3whYoZnI8k X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org It can happen that the parent of a bfqq changes between the moment we decide two queues are worth to merge (and set bic->stable_merge_bfqq) and the moment bfq_setup_merge() is called. This can happen e.g. because the process submitted IO for a different cgroup and thus bfqq got reparented. It can even happen that the bfqq we are merging with has parent cgroup that is already offline and going to be destroyed in which case the merge can lead to use-after-free issues such as: BUG: KASAN: use-after-free in __bfq_deactivate_entity+0x9cb/0xa50 Read of size 8 at addr ffff88800693c0c0 by task runc:[2:INIT]/10544 CPU: 0 PID: 10544 Comm: runc:[2:INIT] Tainted: G E 5.15.2-0.g5fb85fd-default #1 openSUSE Tumbleweed (unreleased) f1f3b891c72369aebecd2e43e4641a6358867c70 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014 Call Trace: dump_stack_lvl+0x46/0x5a print_address_description.constprop.0+0x1f/0x140 ? __bfq_deactivate_entity+0x9cb/0xa50 kasan_report.cold+0x7f/0x11b ? __bfq_deactivate_entity+0x9cb/0xa50 __bfq_deactivate_entity+0x9cb/0xa50 ? update_curr+0x32f/0x5d0 bfq_deactivate_entity+0xa0/0x1d0 bfq_del_bfqq_busy+0x28a/0x420 ? resched_curr+0x116/0x1d0 ? bfq_requeue_bfqq+0x70/0x70 ? check_preempt_wakeup+0x52b/0xbc0 __bfq_bfqq_expire+0x1a2/0x270 bfq_bfqq_expire+0xd16/0x2160 ? try_to_wake_up+0x4ee/0x1260 ? bfq_end_wr_async_queues+0xe0/0xe0 ? _raw_write_unlock_bh+0x60/0x60 ? _raw_spin_lock_irq+0x81/0xe0 bfq_idle_slice_timer+0x109/0x280 ? bfq_dispatch_request+0x4870/0x4870 __hrtimer_run_queues+0x37d/0x700 ? enqueue_hrtimer+0x1b0/0x1b0 ? kvm_clock_get_cycles+0xd/0x10 ? ktime_get_update_offsets_now+0x6f/0x280 hrtimer_interrupt+0x2c8/0x740 Fix the problem by checking that the parent of the two bfqqs we are merging in bfq_setup_merge() is the same. Link: https://lore.kernel.org/linux-block/20211125172809.GC19572@quack2.suse.cz/ CC: stable@vger.kernel.org Fixes: 430a67f9d616 ("block, bfq: merge bursts of newly-created queues") Signed-off-by: Jan Kara --- block/bfq-iosched.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 056399185c2f..0da47f2ca781 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2638,6 +2638,14 @@ bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) if (process_refs == 0 || new_process_refs == 0) return NULL; + /* + * Make sure merged queues belong to the same parent. Parents could + * have changed since the time we decided the two queues are suitable + * for merging. + */ + if (new_bfqq->entity.parent != bfqq->entity.parent) + return NULL; + bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d", new_bfqq->pid);