From nobody Fri May 3 14:21:18 2024 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 D531DC77B62 for ; Tue, 28 Mar 2023 09:45:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232769AbjC1Jog (ORCPT ); Tue, 28 Mar 2023 05:44:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232950AbjC1JoW (ORCPT ); Tue, 28 Mar 2023 05:44:22 -0400 Received: from dggsgout11.his.huawei.com (unknown [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45DBB5BA5; Tue, 28 Mar 2023 02:44:20 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.169]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4Pm4Wz3pNkz4f3wYm; Tue, 28 Mar 2023 17:44:15 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP3 (Coremail) with SMTP id _Ch0CgCnUiDvtiJkYufTFg--.25586S4; Tue, 28 Mar 2023 17:44:16 +0800 (CST) From: Yu Kuai To: xni@redhat.com, song@kernel.org, logang@deltatee.com Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com, yangerkun@huawei.com Subject: [PATCH -next] md: fix regression for null-ptr-deference in __md_stop() Date: Tue, 28 Mar 2023 17:44:00 +0800 Message-Id: <20230328094400.1448955-1-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _Ch0CgCnUiDvtiJkYufTFg--.25586S4 X-Coremail-Antispam: 1UD129KBjvJXoWxGFykAFyUJF48KFy5WrW7urg_yoW5AF17pF WxKF98Gr4kX3yxt3yUAF1kua43Xa48JFZ2ya9xCryrA3ZI9rWDu3WUur1UZFWUCr97t3ZI qw48ZFZrWas0kwUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUyl14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26F4U JVW0owA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oV Cq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0 I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r 4UM4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwCF04k20xvY0x0EwIxG rwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4 vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IY x2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Jr0_Gr1lIxAIcVCF04k26c xKx2IYs7xG6rW3Jr0E3s1lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x02 67AKxVWUJVW8JbIYCTnIWIevJa73UjIFyTuYvjfUoOJ5UUUUU X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Yu Kuai Commit 3e453522593d ("md: Free resources in __md_stop") tried to fix null-ptr-deference for 'active_io' by moving percpu_ref_exit() to __md_stop(), however, the commit also moving 'writes_pending' to __md_stop(), and this will cause mdadm tests broken: BUG: kernel NULL pointer dereference, address: 0000000000000038 Oops: 0000 [#1] PREEMPT SMP CPU: 15 PID: 17830 Comm: mdadm Not tainted 6.3.0-rc3-next-20230324-00009-g5= 20d37 RIP: 0010:free_percpu+0x465/0x670 Call Trace: __percpu_ref_exit+0x48/0x70 percpu_ref_exit+0x1a/0x90 __md_stop+0xe9/0x170 do_md_stop+0x1e1/0x7b0 md_ioctl+0x90c/0x1aa0 blkdev_ioctl+0x19b/0x400 vfs_ioctl+0x20/0x50 __x64_sys_ioctl+0xba/0xe0 do_syscall_64+0x6c/0xe0 entry_SYSCALL_64_after_hwframe+0x63/0xcd And the problem can be reporduced 100% by following test: mdadm -CR /dev/md0 -l1 -n1 /dev/sda --force echo inactive > /sys/block/md0/md/array_state echo read-auto > /sys/block/md0/md/array_state echo inactive > /sys/block/md0/md/array_state Root cause: // start raid raid1_run mddev_init_writes_pending percpu_ref_init // inactive raid array_state_store do_md_stop __md_stop percpu_ref_exit // start raid again array_state_store do_md_run raid1_run mddev_init_writes_pending if (mddev->writes_pending.percpu_count_ptr) // won't reinit // inactive raid again ... percpu_ref_exit -> null-ptr-deference Before the commit, 'writes_pending' is exited when mddev is freed, and it's safe to restart raid because mddev_init_writes_pending() already make sure that 'writes_pending' will only be initialized once. Fix the prblem by moving 'writes_pending' back, it's a litter hard to find the relationship between alloc memory and free memory, however, code changes is much less and we lived with this for a long time already. Fixes: 3e453522593d ("md: Free resources in __md_stop") Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni --- drivers/md/md.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 161231e01faa..06f262050400 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6265,7 +6265,6 @@ static void __md_stop(struct mddev *mddev) module_put(pers->owner); clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); =20 - percpu_ref_exit(&mddev->writes_pending); percpu_ref_exit(&mddev->active_io); bioset_exit(&mddev->bio_set); bioset_exit(&mddev->sync_set); @@ -6278,6 +6277,7 @@ void md_stop(struct mddev *mddev) */ __md_stop_writes(mddev); __md_stop(mddev); + percpu_ref_exit(&mddev->writes_pending); } =20 EXPORT_SYMBOL_GPL(md_stop); @@ -7848,6 +7848,7 @@ static void md_free_disk(struct gendisk *disk) { struct mddev *mddev =3D disk->private_data; =20 + percpu_ref_exit(&mddev->writes_pending); mddev_free(mddev); } =20 --=20 2.39.2