Re: [PATCH 5.17 000/772] 5.17.14-rc1 review

Coly Li
2022-06-18T11:57:18Z

> 2022年6月18日 19:37，Pavel Machek <pavel@ucw.cz> 写道：
>
> Hi!
>
>>>> Fixes: bc082a55d25c ("bcache: fix inaccurate io state for detached
>>> ...
>>>
>>>> +++ b/drivers/md/bcache/request.c
>>>> @@ -1107,6 +1107,12 @@ static void detached_dev_do_request(struct
>>>> bcache_device *d, struct bio *bio,
>>>> * which would call closure_get(&dc->disk.cl)
>>>> */
>>>> ddip = kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO);
>>>> + if (!ddip) {
>>>> + bio->bi_status = BLK_STS_RESOURCE;
>>>> + bio->bi_end_io(bio);
>>>> + return;
>>>> + }
>>>> +
>>>> ddip->d = d;
>>>> /* Count on the bcache device */
>>>> ddip->orig_bdev = orig_bdev;
>>>>
>>>
>>> So... for patch to make any difference, memory allocation has to fail
>>> and ddip has to be NULL.
>>>
>>> Before the patch, it would oops in "ddip->d = d;". With the patch, you
>>> do some kind of error handling. Even if it is buggy, it should not do
>>> more harm than immediate oops.
>>
>> I just receive this single email and don’t have any idea for the context and what the problem is. Where can I see the whole conversation?
>>
>
> Discussion happened on stable@vger.kernel.org mailing lists, archives
> should be easily available. Copy went to lkml, too.

Hi Pavel and Greg,

Thanks for the hint, I see the context. I cannot tell the direct reason of the kfence regression, but it is worthy to have this patch in,
- commit 7d6b902ea0e0 ("bcache: memset on stack variables in bch_btree_check() and bch_sectors_dirty_init()”)

I am not sure whether it is directly related to the kfence issue, it corrects potential unexpected stack state in some condition. Hope it may help a bit.

Thanks.

Coly Li