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SubjectRe: [PATCH] drbd: fix access after free
Jens, I had hoped you'd apply this "oneliner" into 4.18 already?
Did you miss it?

Cheers,

Lars


On Mon, Jun 25, 2018 at 11:39:52AM +0200, Lars Ellenberg wrote:
> bio_put(req->private_bio);
> - req->private_bio = ERR_PTR(error);
> + req->private_bio = ERR_PTR(bio->bi_error);
>
> Which introduces an access after free,
> because it was non obvious that req->private_bio == bio.

> bio_put(req->private_bio);
> req->private_bio = ERR_PTR(blk_status_to_errno(bio->bi_status));

> Should also go into stable since 4.3, with the trivial change around 4.13.
>
> Cc: stable@vger.kernel.org
> Fixes: 4246a0b63bd8 block: add a bi_error field to struct bio
> Reported-by: Sarah Newman <srn@prgmr.com>
> Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
> ---
> drivers/block/drbd/drbd_worker.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
> index 1476cb3439f4..5e793dd7adfb 100644
> --- a/drivers/block/drbd/drbd_worker.c
> +++ b/drivers/block/drbd/drbd_worker.c
> @@ -282,8 +282,8 @@ void drbd_request_endio(struct bio *bio)
> what = COMPLETED_OK;
> }
>
> - bio_put(req->private_bio);
> req->private_bio = ERR_PTR(blk_status_to_errno(bio->bi_status));
> + bio_put(bio);
>
> /* not req_mod(), we need irqsave here! */
> spin_lock_irqsave(&device->resource->req_lock, flags);
> --
> 2.17.1

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