Re: [PATCH v2] md: raid1: fix potential OOB in raid1_remove_disk()

From: Yu Kuai <yukuai1@huaweicloud.com>
To: Song Liu <song@kernel.org>, Yu Kuai <yukuai1@huaweicloud.com>
Cc: Zhang Shurong <zhang_shurong@foxmail.com>,
	linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
	"yukuai (C)" <yukuai3@huawei.com>
Subject: Re: [PATCH v2] md: raid1: fix potential OOB in raid1_remove_disk()
Date: Mon, 31 Jul 2023 09:07:57 +0800	[thread overview]
Message-ID: <52ddb065-e778-53d0-9679-7a6879e8a8e9@huaweicloud.com> (raw)
In-Reply-To: <CAPhsuW6UnqTowo0CZVZXcb_Z=OjV5xFwYqD1O6FO3CLqiKx2DQ@mail.gmail.com>

Hi,

在 2023/07/29 18:49, Song Liu 写道:
> On Mon, Jul 24, 2023 at 10:12 AM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>
>> 在 2023/07/22 15:53, Zhang Shurong 写道:
>>> If rddev->raid_disk is greater than mddev->raid_disks, there will be
>>> an out-of-bounds in raid1_remove_disk(). We have already found
>>> similar reports as follows:
>>>
>>> 1) commit d17f744e883b ("md-raid10: fix KASAN warning")
>>> 2) commit 1ebc2cec0b7d ("dm raid: fix KASAN warning in raid5_remove_disk")
>>>
>>> Fix this bug by checking whether the "number" variable is
>>> valid.
>>
>> LGTM
>>
>> Reviewed-by: Yu Kuai <yukuai3@huawei.com>
>>>
>>> Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
>>> ---
>>> Changes in v2:
>>>    - Using conf->raid_disks instead of mddev->raid_disks.
>>>
>>>    drivers/md/raid1.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
>>> index dd25832eb045..80aeee63dfb7 100644
>>> --- a/drivers/md/raid1.c
>>> +++ b/drivers/md/raid1.c
>>> @@ -1829,6 +1829,10 @@ static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
>>>        struct r1conf *conf = mddev->private;
>>>        int err = 0;
>>>        int number = rdev->raid_disk;
>>> +
>>> +     if (unlikely(number >= conf->raid_disks))
>>> +             goto abort;
> 
> We need err = -EINVAL here.

I think return 0 is right here, so that caller can remove this rdev
from array successfully, this only need to return error for the case
-EBUSY.

Thanks,
Kuai

> 
>>> +
>>>        struct raid1_info *p = conf->mirrors + number;
>>>
>>>        if (rdev != p->rdev)
>>>
>>
> .
>