2022-03-25 20:12:21

by Xiaoke Wang

Subject: [PATCH] bcache: add a check for the return of kzalloc()

From: Xiaoke Wang <[email protected]>

kzalloc() is a memory allocation function which can return NULL when
some internal memory errors happen. So it is better to check it to
prevent potential wrong memory access.

Signed-off-by: Xiaoke Wang <[email protected]>
---
Note: I just roughly handled the error and this seems to affect the
original functionality. If this cannot fail, maybe the tag
`__GFP_NOFAIL` should be considered.
drivers/md/bcache/request.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 6d1de88..1dc9821 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -1107,14 +1107,16 @@ 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);
- ddip->d = d;
- /* Count on the bcache device */
- ddip->orig_bdev = orig_bdev;
- ddip->start_time = start_time;
- ddip->bi_end_io = bio->bi_end_io;
- ddip->bi_private = bio->bi_private;
- bio->bi_end_io = detached_dev_end_io;
- bio->bi_private = ddip;
+ if (ddip) {
+ ddip->d = d;
+ /* Count on the bcache device */
+ ddip->orig_bdev = orig_bdev;
+ ddip->start_time = start_time;
+ ddip->bi_end_io = bio->bi_end_io;
+ ddip->bi_private = bio->bi_private;
+ bio->bi_end_io = detached_dev_end_io;
+ bio->bi_private = ddip;
+ }

if ((bio_op(bio) == REQ_OP_DISCARD) &&
!blk_queue_discard(bdev_get_queue(dc->bdev)))
--

2022-04-07 21:18:24

by Coly Li

Subject: Re: [PATCH] bcache: add a check for the return of kzalloc()

On 3/25/22 11:27 AM, [email protected] wrote:
> From: Xiaoke Wang <[email protected]>
>
> kzalloc() is a memory allocation function which can return NULL when
> some internal memory errors happen. So it is better to check it to
> prevent potential wrong memory access.
>
> Signed-off-by: Xiaoke Wang <[email protected]>
> ---
> Note: I just roughly handled the error and this seems to affect the
> original functionality. If this cannot fail, maybe the tag
> `__GFP_NOFAIL` should be considered.

The error handling is incorrect indeed. And IIRC there is someone else
already fixes it properly and the patch is not upstream yet.

Thanks.


Coly Li


> drivers/md/bcache/request.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index 6d1de88..1dc9821 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -1107,14 +1107,16 @@ 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);
> - ddip->d = d;
> - /* Count on the bcache device */
> - ddip->orig_bdev = orig_bdev;
> - ddip->start_time = start_time;
> - ddip->bi_end_io = bio->bi_end_io;
> - ddip->bi_private = bio->bi_private;
> - bio->bi_end_io = detached_dev_end_io;
> - bio->bi_private = ddip;
> + if (ddip) {
> + ddip->d = d;
> + /* Count on the bcache device */
> + ddip->orig_bdev = orig_bdev;
> + ddip->start_time = start_time;
> + ddip->bi_end_io = bio->bi_end_io;
> + ddip->bi_private = bio->bi_private;
> + bio->bi_end_io = detached_dev_end_io;
> + bio->bi_private = ddip;
> + }
>
> if ((bio_op(bio) == REQ_OP_DISCARD) &&
> !blk_queue_discard(bdev_get_queue(dc->bdev)))