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Subject: Re: [PATCH] md: bcache: check the return value of kzalloc() in
 detached_dev_do_request()
To:     Coly Li <colyli@suse.de>
Cc:     linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org,
        kent.overstreet@gmail.com
References: <20220225082048.19524-1-baijiaju1990@gmail.com>
 <f9a07f10-9d9d-de94-64b9-acf722cea8cd@suse.de>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <35f6f57d-5253-bd49-34ba-be919f3a36d9@gmail.com>
Date:   Thu, 3 Mar 2022 09:44:54 +0800
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On 2022/3/2 18:11, Coly Li wrote:
> On 2/25/22 4:20 PM, Jia-Ju Bai wrote:
>> The function kzalloc() in detached_dev_do_request() can fail, so its
>> return value should be checked.
>>
>> Fixes: bc082a55d25c (bcache: fix inaccurate io state for detached 
>> bcache devices)
>> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>> ---
>>   drivers/md/bcache/request.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
>> index d15aae6c51c1..1b5ccfa93b8c 100644
>> --- a/drivers/md/bcache/request.c
>> +++ b/drivers/md/bcache/request.c
>> @@ -1107,6 +1107,8 @@ 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);
>
> Yes this is a potential problem, may result NULL pointer deference.
>
>
>> +    if (!ddip)
>> +        return;
>
> The fix here is incorrect. A proper way to fix might be something like 
> this,
>
>     if (!ddip) {
>
>         bio->bi_status = BLK_STS_RESOURCE;
>
>         bio->bi_end_io(bio);
>
>         return;
>
>     }
>
>
> The orignal patch will make I/O task be in sleep forever.
>
>>       ddip->d = d;
>>       /* Count on the bcache device */
>>       ddip->orig_bdev = orig_bdev;
>

Hi Coly,

Thanks for the advice!
I will send a V2 patch.


Best wishes,
Jia-Ju Bai