Re: [PATCH] block: make sure that bvec length can't be overflowed

[Hannes Reinecke <hare@suse.de>]

On 4/16/19 5:38 PM, Ming Lei wrote:
> bvec->bv_offset may be bigger than PAGE_SIZE sometimes, such as,
> when one bio is splitted in the middle of one bvec via bio_split(),
> and bi_iter.bi_bvec_done is used to build offset of the 1st bvec of
> remained bio.
> 
> So we have to make sure that every bvec's offset is less than
> PAGE_SIZE from bio_for_each_segment().
> 
> This patch fixes this issue reported by Zhang Yi When running nvme/011.
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Yi Zhang <yi.zhang@redhat.com>
> Reported-by: Yi Zhang <yi.zhang@redhat.com>
> Fixes: 6dc4f100c175 ("block: allow bio_for_each_segment_all() to iterate over multi-page bvec")
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>   include/linux/bvec.h | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/bvec.h b/include/linux/bvec.h
> index 3bc91879e1e2..f179b370066f 100644
> --- a/include/linux/bvec.h
> +++ b/include/linux/bvec.h
> @@ -160,8 +160,9 @@ static inline void bvec_advance(const struct bio_vec *bvec,
>   		bv->bv_page = nth_page(bv->bv_page, 1);
>   		bv->bv_offset = 0;
>   	} else {
> -		bv->bv_page = bvec->bv_page;
> -		bv->bv_offset = bvec->bv_offset;
> +		bv->bv_page = bvec_nth_page(bvec->bv_page, bvec->bv_offset /
> +					    PAGE_SIZE);
> +		bv->bv_offset = bvec->bv_offset % PAGE_SIZE;
>   	}
>   	bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
>   			   bvec->bv_len - iter_all->done);
> 
Looks okay.

Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@suse.de                              +49 911 74053 688
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