From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sg-3-41.ptr.tlmpb.com (sg-3-41.ptr.tlmpb.com [101.45.255.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 841293BD22E for ; Sun, 4 Oct 2026 15:52:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=101.45.255.41 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791129133; cv=none; b=X4aGB1ND485duv6LxV7vFVreP5ulknAlDZdwkNkE8KcbwmLC55IN6db9Tu5RwfphaeAIB8bXuxawSBzcU9WOD7ePq+lKCG+iH47QEIMOJXyG3XDGkWp1e2xrqcvTPdo0VJZgPCHFecVgtqL0df0Q8q1MQtT3gxvx60KRPBb7e8c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791129133; c=relaxed/simple; bh=JYfSDbevSyklrFpxJ/wTrpgYy/neyqm9a6uWSluHa+U=; h=Content-Type:Subject:To:Cc:From:Mime-Version:References:Date: Message-Id:In-Reply-To; b=h7VCme+UVpQXdLJjbnPjRohEbXULfS/Dfd9BUBQ+hhxIHhjFkyBtCKmyQbh+SR39mk51ZDKF968nTWYX08EsFT7CtZRZYBjwvPh8yAKLZj6MVCdKGWVE9aAODdfMGysUrEs3cmbMr+KgVq9DkmWjYQS59yBXdjo2tJ0tcRpyjpg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=fygo.io; spf=pass smtp.mailfrom=fygo.io; dkim=pass (2048-bit key) header.d=fygo-io.20200929.dkim.larksuite.com header.i=@fygo-io.20200929.dkim.larksuite.com header.b=L3Ao1wLJ; arc=none smtp.client-ip=101.45.255.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=fygo.io Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fygo.io Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fygo-io.20200929.dkim.larksuite.com header.i=@fygo-io.20200929.dkim.larksuite.com header.b="L3Ao1wLJ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=s1; d=fygo-io.20200929.dkim.larksuite.com; t=1791129083; h=from:subject:mime-version:from:date:message-id:subject:to:cc: reply-to:content-type:mime-version:in-reply-to:message-id; bh=N0IBTDh9NOUscIgRtt+2unFn8HLJ72nJ0CB0mU61Q9Q=; b=L3Ao1wLJioIMwWdagYezGOv0RneyqwjZ6HcbRdW7BH26SPOTD8YYQmD2iC9Te2Fm7ZZtOt EQCtIz6Nt0drrbBZ7bCSD3Z+y1R4se8Hb6B7HPdYZuX5z5TythzmgYVZO6+QGyn0lbuMQ9 fRJ9MWqYeqg+UUZN1WzzvwhuDJw2IEs0xxWU/HLJfp5rh2vJQ8fM4muwO5ZlEY0VToSwaj SBfSWVOv9OYRGUmMM+oeIyrtY0C1ATPga3LOVKfmpC2K7ywj7GuH2o1fYIqY/uHr9gW/uR v4g5lbCMfo/mQsaujV8lupc/wRsuhrCQPcrYT2Zs2GTUQhZbWbqj8pUIVVCeFA== Content-Type: text/plain; charset=UTF-8 Subject: Re: [PATCH v5] md: Fix the null-ptr-deref of 'mddev->private' while submitting IO Content-Transfer-Encoding: quoted-printable User-Agent: Mozilla Thunderbird To: "Zhihao Cheng" , , , , , , "yu kuai" Cc: , , , "linux-raid@vger.kernel.org" From: "yu kuai" Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260922030538.1634904-1-chengzhihao1@huawei.com> Received: from [192.168.1.104] ([39.182.0.177]) by smtp.larksuite.com with ESMTPS; Sun, 04 Oct 2026 15:51:22 +0000 Reply-To: yukuai@fygo.io Date: Sun, 4 Oct 2026 23:51:18 +0800 Message-Id: In-Reply-To: <20260922030538.1634904-1-chengzhihao1@huawei.com> X-Lms-Return-Path: X-Original-From: yu kuai Hi, =E5=9C=A8 2026/9/22 11:05, Zhihao Cheng =E5=86=99=E9=81=93: > 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=3D22202= 0 > > 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 > v4->v5: > 1. Skip checking '!md_is_rdwr' only for inactive case > drivers/md/md.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) This patch is missed because it's not in patchwork. :( Applied to md-7.4 > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index 680b34a63cb3..02798f2dbf0e 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -414,6 +414,20 @@ bool md_handle_request(struct mddev *mddev, struct b= io *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 *= buf, size_t len) > case readonly: > case inactive: > case read_auto: > - if (!mddev->pers || !md_is_rdwr(mddev)) > + if (!mddev->pers || (st !=3D inactive && !md_is_rdwr(mddev))) > 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 Thanks, Kuai