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SubjectRe: [PATCH v2 1/4] md/raid10: fix null-ptr-deref of mreplace in raid10_sync_request
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在 2023/5/27 5:38, Song Liu 写道:
> On Fri, May 26, 2023 at 12:47 AM <linan666@huaweicloud.com> wrote:
>>
>> From: Li Nan <linan122@huawei.com>
>>
>> need_replace will be set to 1 if no-Faulty mreplace exists, and mreplace
>> will be deref later. However, the latter check of mreplace might set
>> mreplace to NULL, null-ptr-deref occurs if need_replace is 1 at this time.
>>
>> Fix it by merging two checks into one. And replace 'need_replace' with
>> 'mreplace' because their values are always the same.
>>
>> Fixes: ee37d7314a32 ("md/raid10: Fix raid10 replace hang when new added disk faulty")
>> Signed-off-by: Li Nan <linan122@huawei.com>
>> ---
>> drivers/md/raid10.c | 13 +++++--------
>> 1 file changed, 5 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
>> index 4fcfcb350d2b..e21502c03b45 100644
>> --- a/drivers/md/raid10.c
>> +++ b/drivers/md/raid10.c
>> @@ -3438,7 +3438,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>> int must_sync;
>> int any_working;
>> int need_recover = 0;
>> - int need_replace = 0;
>> struct raid10_info *mirror = &conf->mirrors[i];
>> struct md_rdev *mrdev, *mreplace;
>>
>> @@ -3451,10 +3450,10 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>> !test_bit(In_sync, &mrdev->flags))
>> need_recover = 1;
>> if (mreplace != NULL &&
>> - !test_bit(Faulty, &mreplace->flags))
>> - need_replace = 1;
>> + test_bit(Faulty, &mreplace->flags))
>> + mreplace = NULL;
>>
>> - if (!need_recover && !need_replace) {
>> + if (!need_recover && !mreplace) {
>> rcu_read_unlock();
>> continue;
>> }
>> @@ -3470,8 +3469,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
>> rcu_read_unlock();
>> continue;
>> }
>
> To make sure I understand the issue correctly:
>
> The null-ptr-deref only happens when the Faulty bit was set after the
> last check and before this check below, right?
>

Yes. I will improve log in next version.

--
Thanks,
Nan

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