From mboxrd@z Thu Jan 1 00:00:00 1970 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 792A83AA1BB; Fri, 18 Sep 2026 06:20:12 +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=1789712429; cv=none; b=Jxb5C7+/YwlQzSJntky21Firi5D26JVcQZEgIVJG7PYaDiqtIR41ZUxSuwxgOkW9JrsF9bCKldv7U9Todbk3mzpIUfL2kTSkOnKqEqAr43fM9iGUzRVN9SdNh83CCxWAs+e6uQpZezaYA5QqJ7oVgTSaz5VHBj7XGmxkEQQTaiQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789712429; c=relaxed/simple; bh=y7qYGOqBHTkXcv+UGyVR3fatY+b21N34bZspwFXzlI8=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=BYJZSnukFirPx+lcXPYKGtHU3m/xe1pgbCDdYzOeT2bWaH7QAgUB7NBIZwkb/+5Ae9uy8Elg+D3AheiR4fCqk6yj1FG8G8zQBp8puTfiokgcViwIXtoiulLMqUgPvmUM11Ti1rv4rCN0fZsjHKIPnwEegjRtKEwRIn3NH86ZAww= 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=YwuI63Jz; 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="YwuI63Jz" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=/EmTRV68EuwkaVOnj6HPetBktycK3QdXzrHOdjiyXcM=; b=YwuI63Jz9js7cJjl844wtkdaA1pbgtEwRz4yxIlQropQr9MLOo2hrouTxjT1OsT2uE6For5T7 BK4gjYGejgTgD4VJeWyFRvjnGyvYpSVFqR0tns764NOEYTiwh9zSLCyBjg6JIR9nz/y1NsCrPPO AJGilsbaSsCt9fhC0YNaSBU= Received: from mail.maildlp.com (unknown [172.19.162.144]) by canpmsgout04.his.huawei.com (SkyGuard) with ESMTPS id 4hmMdM74mZz1prLc; Fri, 18 Sep 2026 14:08:55 +0800 (CST) Received: from whupemo200011.china.huawei.com (unknown [7.152.185.179]) by mail.maildlp.com (Postfix) with ESMTPS id 2E9F34056D; Fri, 18 Sep 2026 14:19:57 +0800 (CST) Received: from [10.174.178.46] (10.174.178.46) 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; Fri, 18 Sep 2026 14:19:55 +0800 Subject: Re: [PATCH v2] md: Fix the null-ptr-deref of 'mddev->private' while submitting IO To: , , , , , CC: , , , References: <20260917024205.2331019-1-chengzhihao1@huawei.com> From: Zhihao Cheng Message-ID: Date: Fri, 18 Sep 2026 14:19:50 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To whupemo200011.china.huawei.com (7.152.185.179) 在 2026/9/18 14:06, yu kuai 写道: > Hi, > > 在 2026/9/17 10:42, Zhihao Cheng 写道: >> 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 = open(/dev/md0, O_RDWR) >> P2 (forked from P1, fd' <= 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 = 1, >> // because md_open() is only called >> // once in P1->open >> do_md_stop >> __md_stop >> mddev->private = NULL >> >> conf = 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=222020 >> >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >> Reported-by: syzbot+3fe892ea5fc292e1353f@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=3fe892ea5fc292e1353f >> Signed-off-by: Zhihao Cheng >> --- >> v1->v2: >> 1. Add 'mddev->pers != 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 *buf, size_t len) >> { >> int err = 0; >> enum array_state st = match_word(buf, array_states); >> + unsigned int noio_flags = 0; >> + bool suspend = false; >> >> /* No lock dependent actions */ >> switch (st) { >> @@ -4666,9 +4682,11 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len) >> case broken: /* cannot be set */ >> case bad_word: >> return -EINVAL; >> + case inactive: >> case clear: >> + suspend = 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 *buf, size_t len) >> spin_unlock(&mddev->lock); >> return err ?: len; >> } >> - err = mddev_lock(mddev); >> + err = suspend ? mddev_suspend_and_lock(mddev) : mddev_lock(mddev); > > Unlike ioctl path, where the checking of opener is just 1, mddev_set_closing_and_sync_blockdev() here > already check there is no opener, so there can't be any IO inflight. Hi, yukuai I thought of a scene. If someone open '/dev/md0, write(buffer) 4K, and close the corresponding fd. Then writeback kworker submit IO, array_state_store will pass the mddev_set_closing_and_sync_blockdev() check, which could lead to the similar problem. > >> if (err) >> return err; >> + if (suspend) >> + noio_flags = memalloc_noio_save(); >> >> switch (st) { >> case inactive: >> @@ -4775,7 +4795,12 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len) >> mddev->hold_active = 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); >> + } >> >> if (st == readonly || st == read_auto || st == inactive || >> (err && st == 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; >