linux-kernel - Re: [PATCH] md: bcache: check the return value of kzalloc() in detached_dev_do

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Date:   Wed, 2 Mar 2022 18:11:29 +0800
From:   Coly Li <colyli@...e.de>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
        kent.overstreet@...il.com
Subject: Re: [PATCH] md: bcache: check the return value of kzalloc() in
 detached_dev_do_request()

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@...nghua.edu.cn>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.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;