From nobody Thu Sep 24 21:19:58 2026 Received: from canpmsgout07.his.huawei.com (canpmsgout07.his.huawei.com [113.46.200.222]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 33A953DC4B3; Sun, 20 Sep 2026 06:45:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.222 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789886710; cv=none; b=q0ancMBIXisu3/c/TWC3LarrSfdC8NTFXb7ySDEVS5AzCSWxSUvTJLvaBwrXmVARReGNKpuqOiE3Yh+k+UScxvmHfx6KwpTBxeEj+9Y7JXQLTHe2x87siupqYwsoQCJUO+HveHCzKXNDlLfzYCagfdmgu+nm1XMzT2WCIWOA28I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789886710; c=relaxed/simple; bh=B8BAjswNIsS2gLDIxmLgpF2MHTyLD+ZWXR2OZH4QHGE=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=EGZdubrDZ4YhepQ/6xJ4HfHYWUTJp4KqY4rhH+Q5QJWB/KphSuYPYxJ5jfZhtglGW0kHop7Tv+DKRqHtZM3jIzjGePHd4MjZyQkFHeVNhiB/H7no8u9ZI/d815kYBFH/PuGiSWy/HZayyk+KX0y7wxUDO03IGwI87r4yIR0d94k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=ePCfXPOL; arc=none smtp.client-ip=113.46.200.222 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="ePCfXPOL" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=HfZOyzQc0uYKBZ1L7tWk8X5vgznY3cRdXLJwGK+D0ZA=; b=ePCfXPOLdKUz0P1mPkQbJuzmLRCCZPpDI9Tg8oKBvstJYFyxGIrXHgmpsAU8Rd8/vx7GAK5Dj 44BCIfzbaW/2Ud31lqrHE/7xC52ukWFBMW+skt1AroxfLUgWqmslsODQmQGMmjlJ3SgiXA9yt2s +KIUTdO/QRL211EEeN0tyC8= Received: from mail.maildlp.com (unknown [172.19.162.92]) by canpmsgout07.his.huawei.com (SkyGuard) with ESMTPS id 4hnc5P3mTZzLlX2; Sun, 20 Sep 2026 14:34:01 +0800 (CST) Received: from whupemo200011.china.huawei.com (unknown [7.152.185.179]) by mail.maildlp.com (Postfix) with ESMTPS id 926BF40586; Sun, 20 Sep 2026 14:45:02 +0800 (CST) Received: from huawei.com (10.50.85.155) by whupemo200011.china.huawei.com (7.152.185.179) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Sun, 20 Sep 2026 14:45:01 +0800 From: Zhihao Cheng To: , , , , , CC: , , , , Subject: [PATCH v4] md: Fix the null-ptr-deref of 'mddev->private' while submitting IO Date: Sun, 20 Sep 2026 14:37:04 +0800 Message-ID: <20260920063704.3809608-1-chengzhihao1@huawei.com> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems500001.china.huawei.com (7.221.188.70) To whupemo200011.china.huawei.com (7.152.185.179) Content-Type: text/plain; charset="utf-8" Concurrent processes md_stop and IO submitting could trigger a null-ptr-deref of 'mddev->private': BUG: kernel NULL pointer dereference, address: 0000000000000070 RIP: 0010:_wait_barrier+0x2f/0x250 Call Trace: raid1_make_request+0x150/0xf50 md_handle_request+0x104/0x530 md_submit_bio+0x76/0x130 submit_bio+0xdd/0x250 submit_bio_wait+0x1f/0x40 __blkdev_direct_IO_simple+0x1f6/0x370 blkdev_write_iter+0x3b2/0x520 ksys_write+0x7d/0x190 P1 fd =3D open(/dev/md0, O_RDWR) P2 (forked from P1, fd' <=3D fd) write(fd) submit_bio md_handle_request raid1_make_request raid1_write_request ioctl(fd, STOP_ARRAY) mddev_set_closing_and_sync_blockdev // check passed, mddev->openers =3D 1, // because md_open() is only called // once in P1->open do_md_stop __md_stop mddev->private =3D NULL conf =3D mddev->private // NULL wait_barrier(conf, sector) // null-ptr-deref ! It is a common problem for raid0/1/10/5, and __md_stop could be triggered by several paths(eg. ioctl, sysfs, ->dtr). Fix it by replacing mddev_lock() with mddev_suspend_and_lock() for all __md_stop() callers. The caller array_state_store() is guaranteed by the check mddev_set_closing_and_sync_blockdev(mddev, 0), we just need to remove the check '!md_is_rdwr'. For example, someone open /dev/mdx, write something and close /dev/mdx, it won't trigger the problem, all dirty pages can be flushed before mddev->openers decrement. The caller dm_table_destroy() is guaranteed being invoked with device suspended, so raid_dtr() could keep using mddev_lock_nointr(). Besides, fail the submitting IO in md_handle_request() if the 'mddev->pers' becomes NULL. Fetch a reproducer in https://bugzilla.kernel.org/show_bug.cgi?id=3D222020 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+3fe892ea5fc292e1353f@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D3fe892ea5fc292e1353f Signed-off-by: Zhihao Cheng --- v1->v2: 1. Add 'mddev->pers !=3D NULL' check before make_request 2. Delete dm-raid caller(->dtr) modifications 3. Move memalloc_noio_restore after mddev_unlock_and_resume v2->v3: 1. Remove modifications in array_state_store() 2. update commit msg v3->v4: 1. Remove '!md_is_rdwr' check from array_state_store() 2. update commit msg drivers/md/md.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 680b34a63cb3..d81f5bf3bffe 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -414,6 +414,20 @@ bool md_handle_request(struct mddev *mddev, struct bio= *bio) if (!percpu_ref_tryget_live(&mddev->active_io)) goto check_suspended; } + if (!mddev->pers) { + /* + * The __md_stop() sets 'mddev->private' to NULL during + * the IO submitting, check 'mddev->pers' before the IO + * being processed by specific driver to avoid the + * null-ptr-deref of 'mddev->'. The check is + * safe because the IO has got the 'mddev->active_io' + * reference, and all __md_stop() callers will wait for + * the reference to be zero. + */ + bio_io_error(bio); + percpu_ref_put(&mddev->active_io); + return true; + } if (!mddev->pers->make_request(mddev, bio)) { percpu_ref_put(&mddev->active_io); if (mddev_is_dm(mddev) && mddev->pers->prepare_suspend) @@ -4670,7 +4684,7 @@ array_state_store(struct mddev *mddev, const char *bu= f, size_t len) case readonly: case inactive: case read_auto: - if (!mddev->pers || !md_is_rdwr(mddev)) + if (!mddev->pers) break; /* write sysfs will not open mddev and opener should be 0 */ err =3D mddev_set_closing_and_sync_blockdev(mddev, 0); @@ -8299,6 +8313,7 @@ static bool md_ioctl_need_suspend(unsigned int cmd) case HOT_REMOVE_DISK: case SET_BITMAP_FILE: case SET_ARRAY_INFO: + case STOP_ARRAY: return true; default: return false; --=20 2.52.0