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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37A95C4167B for ; Fri, 14 Jan 2022 17:02:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243697AbiANRCb (ORCPT ); Fri, 14 Jan 2022 12:02:31 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:35216 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243695AbiANRCa (ORCPT ); Fri, 14 Jan 2022 12:02:30 -0500 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 35EC6219B1; Fri, 14 Jan 2022 17:02:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1642179749; 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=fEP19GZFNu7CiMzyrNWes3nEi1AFHt/7bVN2BDWD/uTgZSVkvi6E0SUuGqBkN/HXMb8SqS kYKe+wIEJFBONj/AInoyP97JxkN9X6P/PrWiADoT+dOu6K5WDUfqh/oUUUfTik0b1yevA5 tT2P+IapWYkgguyJJld/QRmQcGkkrQw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1642179749; 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=GBefCU+JD81UaHLuTumy18++m6stUD1pT0FPJ3THkONY8aATUBb+2qqQcxf0wD5E2bJ7Yl pZvYefRyVi2wUfCw== Received: from quack3.suse.cz (unknown [10.100.224.230]) (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 A96EEA3B84; Fri, 14 Jan 2022 17:02:26 +0000 (UTC) Received: by quack3.suse.cz (Postfix, from userid 1000) id 5D016A05E2; Fri, 14 Jan 2022 18:02:09 +0100 (CET) From: Jan Kara To: Cc: Paolo Valente , Jens Axboe , "yukuai (C)" , Jan Kara , stable@vger.kernel.org Subject: [PATCH 2/4] bfq: Avoid merging queues with different parents Date: Fri, 14 Jan 2022 18:01:54 +0100 Message-Id: <20220114170209.8606-2-jack@suse.cz> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20220114164215.28972-1-jack@suse.cz> References: <20220114164215.28972-1-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/ZEDZAcsmYgBh4ayCCr2kJ3pthS1i4guH+kNkcoxQDTHDYlhq+Qn6 JBmDeFCJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCYeGsggAKCRCcnaoHP2RA2fc+CA Dndw74mFYFk1iVQeGLoVZh7PofJJRP/Jnt4PETNUFUoqdQIenKaSudVxAGs7yOIETtrXdwjZjXZF97 Ogd7YaYibrFHvHyekvH5tM1p9kRjJHIb7SzQhTjavAAhJY8uawj3sOB6yj4Rxf94MwAPDQXi9bcVQe +4ILdKK10w2mh0mUDKWax5QorLDdCh/bOKc9Lvlg8SnoP6ywXXjfs0C1YM02+JIt5BaM5w7Ou83SnF fGkhOI90xBvSMf3XvK15/sK8g2ZRU4dKxFrhnOvKvqXKw4M1gjYddpI3b8Oq14OMlwigbGu93eWSPF T0Br2OCvgtra/u7+s+rds5j4jQ4H1H X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Content-Transfer-Encoding: 8bit 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); -- 2.31.1