[PATCH] nvme: Fix discard buffer overrun

[jianchao.wang]

Hi Keith

Since each discard bio merged into a request is counted as one segment,
why not let blk_rq_nr_discard_segments return numbers of bios directly.

On 02/01/2018 08:01 AM, Keith Busch wrote:
> This patch checks the discard range array bounds before setting it in
> case the driver gets a badly formed request.
> 
> Signed-off-by: Keith Busch <keith.busch at intel.com>
> Cc: Jens Axboe <axboe at kernel.dk>
> ---
>  drivers/nvme/host/core.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 4bfb4ba6cd14..d02906a6dabe 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -518,9 +518,11 @@ static blk_status_t nvme_setup_discard(struct nvme_ns *ns, struct request *req,
>  		u64 slba = nvme_block_nr(ns, bio->bi_iter.bi_sector);
>  		u32 nlb = bio->bi_iter.bi_size >> ns->lba_shift;
>  
> -		range[n].cattr = cpu_to_le32(0);
> -		range[n].nlb = cpu_to_le32(nlb);
> -		range[n].slba = cpu_to_le64(slba);
> +		if (n < segments) {
> +			range[n].cattr = cpu_to_le32(0);
> +			range[n].nlb = cpu_to_le32(nlb);
> +			range[n].slba = cpu_to_le64(slba);
> +		}
>  		n++;
>  	}