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 A797BC43217 for ; Sat, 19 Nov 2022 02:14:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234926AbiKSCOE (ORCPT ); Fri, 18 Nov 2022 21:14:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234266AbiKSCNC (ORCPT ); Fri, 18 Nov 2022 21:13:02 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 939F5776FA; Fri, 18 Nov 2022 18:12:20 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2F6F862831; Sat, 19 Nov 2022 02:12:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74869C433D7; Sat, 19 Nov 2022 02:12:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668823939; bh=FYr04vfyjSoFDAZ0lW1wqrJZDHN6z/tNqY0IwKMY5nw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HJz/FbTQZjHIeaIZjDQf8l8NRWpNyQl1hDmFL/NFdZg606eyIRvCTsUT3IB68tXoU pa0LEM/0duFeZd7aF1gTeypMD+lFDcD2SagfppwPP/LEcz0EDuyUf+ic5WdoAuuVai AnF+zRx+CNsoulOhfrd9/Yn/ya3Udu5VxlvLA0oiBSY8toLVr4URd/ePke0Yjv1NSs cd9CDDbipY3qvMiPd5hCDVRYTgsNSxAqOK/j5cOur+YkCb27P3O/4TSpNQESa4z1JZ 0FEtORlqQcGzTJnVvuByg5ba8wM99cY/Vd+CBByw/+CNuKvDHNEsAn9PMXBxRQs36+ YzYfzXb6T5tTw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Yu Kuai , Jan Kara , Jens Axboe , Sasha Levin , tj@kernel.org, josef@toxicpanda.com, paolo.valente@linaro.org, cgroups@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 6.0 28/44] block, bfq: fix null pointer dereference in bfq_bio_bfqg() Date: Fri, 18 Nov 2022 21:11:08 -0500 Message-Id: <20221119021124.1773699-28-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221119021124.1773699-1-sashal@kernel.org> References: <20221119021124.1773699-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Yu Kuai [ Upstream commit f02be9002c480cd3ec0fcf184ad27cf531bd6ece ] Out test found a following problem in kernel 5.10, and the same problem should exist in mainline: BUG: kernel NULL pointer dereference, address: 0000000000000094 PGD 0 P4D 0 Oops: 0000 [#1] SMP CPU: 7 PID: 155 Comm: kworker/7:1 Not tainted 5.10.0-01932-g19e0ace2ca1d-dirty 4 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-b4 Workqueue: kthrotld blk_throtl_dispatch_work_fn RIP: 0010:bfq_bio_bfqg+0x52/0xc0 Code: 94 00 00 00 00 75 2e 48 8b 40 30 48 83 05 35 06 c8 0b 01 48 85 c0 74 3d 4b RSP: 0018:ffffc90001a1fba0 EFLAGS: 00010002 RAX: ffff888100d60400 RBX: ffff8881132e7000 RCX: 0000000000000000 RDX: 0000000000000017 RSI: ffff888103580a18 RDI: ffff888103580a18 RBP: ffff8881132e7000 R08: 0000000000000000 R09: ffffc90001a1fe10 R10: 0000000000000a20 R11: 0000000000034320 R12: 0000000000000000 R13: ffff888103580a18 R14: ffff888114447000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88881fdc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000094 CR3: 0000000100cdb000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: bfq_bic_update_cgroup+0x3c/0x350 ? ioc_create_icq+0x42/0x270 bfq_init_rq+0xfd/0x1060 bfq_insert_requests+0x20f/0x1cc0 ? ioc_create_icq+0x122/0x270 blk_mq_sched_insert_requests+0x86/0x1d0 blk_mq_flush_plug_list+0x193/0x2a0 blk_flush_plug_list+0x127/0x170 blk_finish_plug+0x31/0x50 blk_throtl_dispatch_work_fn+0x151/0x190 process_one_work+0x27c/0x5f0 worker_thread+0x28b/0x6b0 ? rescuer_thread+0x590/0x590 kthread+0x153/0x1b0 ? kthread_flush_work+0x170/0x170 ret_from_fork+0x1f/0x30 Modules linked in: CR2: 0000000000000094 ---[ end trace e2e59ac014314547 ]--- RIP: 0010:bfq_bio_bfqg+0x52/0xc0 Code: 94 00 00 00 00 75 2e 48 8b 40 30 48 83 05 35 06 c8 0b 01 48 85 c0 74 3d 4b RSP: 0018:ffffc90001a1fba0 EFLAGS: 00010002 RAX: ffff888100d60400 RBX: ffff8881132e7000 RCX: 0000000000000000 RDX: 0000000000000017 RSI: ffff888103580a18 RDI: ffff888103580a18 RBP: ffff8881132e7000 R08: 0000000000000000 R09: ffffc90001a1fe10 R10: 0000000000000a20 R11: 0000000000034320 R12: 0000000000000000 R13: ffff888103580a18 R14: ffff888114447000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88881fdc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000094 CR3: 0000000100cdb000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Root cause is quite complex: 1) use bfq elevator for the test device. 2) create a cgroup CG 3) config blk throtl in CG blkg_conf_prep blkg_create 4) create a thread T1 and issue async io in CG: bio_init bio_associate_blkg ... submit_bio submit_bio_noacct blk_throtl_bio -> io is throttled // io submit is done 5) switch elevator: bfq_exit_queue blkcg_deactivate_policy list_for_each_entry(blkg, &q->blkg_list, q_node) blkg->pd[] = NULL // bfq policy is removed 5) thread t1 exist, then remove the cgroup CG: blkcg_unpin_online blkcg_destroy_blkgs blkg_destroy list_del_init(&blkg->q_node) // blkg is removed from queue list 6) switch elevator back to bfq bfq_init_queue bfq_create_group_hierarchy blkcg_activate_policy list_for_each_entry_reverse(blkg, &q->blkg_list) // blkg is removed from list, hence bfq policy is still NULL 7) throttled io is dispatched to bfq: bfq_insert_requests bfq_init_rq bfq_bic_update_cgroup bfq_bio_bfqg bfqg = blkg_to_bfqg(blkg) // bfqg is NULL because bfq policy is NULL The problem is only possible in bfq because only bfq can be deactivated and activated while queue is online, while others can only be deactivated while the device is removed. Fix the problem in bfq by checking if blkg is online before calling blkg_to_bfqg(). Signed-off-by: Yu Kuai Reviewed-by: Jan Kara Link: https://lore.kernel.org/r/20221108103434.2853269-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/bfq-cgroup.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index 30b15a9a47c4..249f489d115f 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -615,6 +615,10 @@ struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio) struct bfq_group *bfqg; while (blkg) { + if (!blkg->online) { + blkg = blkg->parent; + continue; + } bfqg = blkg_to_bfqg(blkg); if (bfqg->online) { bio_associate_blkg_from_css(bio, &blkg->blkcg->css); -- 2.35.1