On Tue, Feb 19, 2019 at 02:37:02PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> The bio pointer is being null checked hence it can be potentially null,
> however earlier it is being derefefenced on the assignment of front_seg_size.
> Avoid the dereference issue by only assigning front_seg_size after bios has
> been null sanity checked.
>
> Fixes: dcebd755926b ("block: use bio_for_each_bvec() to compute multi-page bvec count")
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> ---
>
> V2: remove front_seg_size assignment when it is declared
>
> ---
> block/blk-merge.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index bed065904677..096947413ea9 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -363,7 +363,7 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
> struct bio_vec bv, bvprv = { NULL };
> int prev = 0;
> unsigned int seg_size, nr_phys_segs;
> - unsigned front_seg_size = bio->bi_seg_front_size;
> + unsigned front_seg_size;
Smatch says bio is non-NULL but I didn't verify by hand.
regards,
dan carpenter
