From nobody Fri Sep 25 03:20:29 2026 Received: from canpmsgout04.his.huawei.com (canpmsgout04.his.huawei.com [113.46.200.219]) (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 F3ADD3A2556; Thu, 17 Sep 2026 02:50:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.219 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789613439; cv=none; b=hX+IRDkYBhr3p/6g013pUPwzImUyvi/CY58BI2Yq6wVylfGyO6VkwEOwN54MEgeEGg0m8OUm4UPRaFIKGJ7p1uZ7Zu52iWVEhzlQcb76sWPKpGFpM3m+uaqrUvyLXhKWpE8AJZe8aUo6KiP7sxJr+CsIGIauAi8zNQu/lJNBDd8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789613439; c=relaxed/simple; bh=aGa+R4CVm6Z7Z5yqLsifND01+EWY62Q5EOY/mDesFm8=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=txsN2p0c3UZwjeVb8W7QRZ6XKn4HOqruhMo913+khWGAStQCvRzWW1GDa9GcYoWUM24rJtfX2nkYmC9OPJgaZDQ7AVKlYK/Hzszm1GsTeDNRroQb86UqYMZH7btAmGI2d4DfP5mLPKVtL0kH1CW5FqBcOmTyxentEdRrhe9wXPs= 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=N0LWOl1r; arc=none smtp.client-ip=113.46.200.219 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="N0LWOl1r" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=tVDvHIicrcLkocQWr0K70sGvb0i/8LhsaYqL36DA6rA=; b=N0LWOl1rUQ+RUXaGdr+aoVGqetXcb4Snbr7hOHxDXp4JGtfs9qVp7+GIzyoDDPzC0+B360DCs ufBC/ljeJasIrwEtoGJTUMcW0hDY/aTlu7tUSIvJGgR0dHCwhufWnrDiySBWJMXAySitkQaX3bc XnagZQ7qeQJxGUfuxXO+gYs= Received: from mail.maildlp.com (unknown [172.19.162.223]) by canpmsgout04.his.huawei.com (SkyGuard) with ESMTPS id 4hlg1b0pTpz1prLc; Thu, 17 Sep 2026 10:38:59 +0800 (CST) Received: from whupemo200011.china.huawei.com (unknown [7.152.185.179]) by mail.maildlp.com (Postfix) with ESMTPS id 966E440561; Thu, 17 Sep 2026 10:49:59 +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; Thu, 17 Sep 2026 10:49:58 +0800 From: Zhihao Cheng To: , , , , , CC: , , , , Subject: [PATCH v2] md: Fix the null-ptr-deref of 'mddev->private' while submitting IO Date: Thu, 17 Sep 2026 10:42:05 +0800 Message-ID: <20260917024205.2331019-1-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: kwepems100002.china.huawei.com (7.221.188.206) 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 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 drivers/md/md.c | 32 +++++++++++++++++++++++++++++--- 1 file changed, 29 insertions(+), 3 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 680b34a63cb3..3dfc34caa2dc 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) @@ -4657,6 +4671,8 @@ array_state_store(struct mddev *mddev, const char *bu= f, size_t len) { int err =3D 0; enum array_state st =3D match_word(buf, array_states); + unsigned int noio_flags =3D 0; + bool suspend =3D false; =20 /* No lock dependent actions */ switch (st) { @@ -4666,9 +4682,11 @@ array_state_store(struct mddev *mddev, const char *b= uf, size_t len) case broken: /* cannot be set */ case bad_word: return -EINVAL; + case inactive: case clear: + suspend =3D true; + fallthrough; case readonly: - case inactive: case read_auto: if (!mddev->pers || !md_is_rdwr(mddev)) break; @@ -4702,9 +4720,11 @@ array_state_store(struct mddev *mddev, const char *b= uf, size_t len) spin_unlock(&mddev->lock); return err ?: len; } - err =3D mddev_lock(mddev); + err =3D suspend ? mddev_suspend_and_lock(mddev) : mddev_lock(mddev); if (err) return err; + if (suspend) + noio_flags =3D memalloc_noio_save(); =20 switch (st) { case inactive: @@ -4775,7 +4795,12 @@ array_state_store(struct mddev *mddev, const char *b= uf, size_t len) mddev->hold_active =3D 0; sysfs_notify_dirent_safe(mddev->sysfs_state); } - mddev_unlock(mddev); + if (suspend) { + mddev_unlock_and_resume(mddev); + memalloc_noio_restore(noio_flags); + } else { + mddev_unlock(mddev); + } =20 if (st =3D=3D readonly || st =3D=3D read_auto || st =3D=3D inactive || (err && st =3D=3D clear)) @@ -8299,6 +8324,7 @@ 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