From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout08.his.huawei.com (canpmsgout08.his.huawei.com [113.46.200.223]) (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 209C437187E; Fri, 18 Sep 2026 06:39:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.223 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789713569; cv=none; b=Ae+MxELezWohUcfVioqqmfIug/tifqUeK4Mh0OhaSPQ1/gUBx0CvEHRWQYZMcxSJSMLb2bXwKrfYAk8ST4yGlFml7NvkKe+RjwVgrtrXKuS4V70MQDwh8oxMjm1We2Xu998gj+OA1MHa7YlyGt6SEusuyDFpw8GYHHCcA8C6Ick= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789713569; c=relaxed/simple; bh=HOhlQQesEuaYkItbWW89rLui6aWKecLLBTrWPnorjYw=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=piGIaQhWJ5zuBo9d9gP4cupxFuUPzRKl/8vhdciq92fMHt5/2k4cvWl7b6DmP+iaceBd+3E2g4ziXQNiaiQvJzfhnm6YRUQx1VC181joASQFIZGq7tqJkkl7SdjmcOO/Loo0wlOf4LEvoQoBwy29LTot+Y04owHWt3durwNLo+Y= 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=CVUcNyHp; arc=none smtp.client-ip=113.46.200.223 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="CVUcNyHp" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=FAdoaLO1tE/u4uqo8rpm5ynOPlWe0f9h04kVn9hHuDY=; b=CVUcNyHpyEFMHDR9Kp/hlncI/4RniTDY442Diym2Jx9WzB10duQrl4PVwD+qc2ghAkAohYOs/ khtd8huvqnmVLtpd67DzxrNp0jKZaokQpJ9d2yZcXDChunlyXswbbyDhCgEYJcDDWPvo770GwE8 1C9ZXrcTH3TlC70NevC6tYk= Received: from mail.maildlp.com (unknown [172.19.163.200]) by canpmsgout08.his.huawei.com (SkyGuard) with ESMTPS id 4hmN3n0rMTzmVX8; Fri, 18 Sep 2026 14:28:21 +0800 (CST) Received: from whupemo200011.china.huawei.com (unknown [7.152.185.179]) by mail.maildlp.com (Postfix) with ESMTPS id 21E7640563; Fri, 18 Sep 2026 14:39:21 +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 14:39:19 +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> <92fd9c95-23db-4bb3-a489-eccc51189bb4@fygo.io> From: Zhihao Cheng Message-ID: <86f05755-0864-2b7c-9a98-830a453f2b62@huawei.com> Date: Fri, 18 Sep 2026 14:39:14 +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: <92fd9c95-23db-4bb3-a489-eccc51189bb4@fygo.io> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To whupemo200011.china.huawei.com (7.152.185.179) 在 2026/9/18 14:30, yu kuai 写道: > Hi, > > 在 2026/9/18 14:19, Zhihao Cheng 写道: >> 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. > This should not happen, that last one to close /dev/md0 will wait for > full disk flush to be done. Makes sense, sync_blockdev will be called in close process. >>> >>>>        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; >>> >>