Re: [PATCH v2 2/2] lightnvm: pblk: Ensure that bio is not freed on recovery

["Matias Bjørling" <mb@lightnvm.io>]

On 12/07/2018 09:25 AM, Igor Konopko wrote:
> When we are using PBLK with 0 sized metadata during recovery
> process we need to reference a last page of bio. Currently
> KASAN reports use-after-free in that case, since bio is
> freed on IO completion.
> 
> This patch adds addtional bio reference to ensure, that we
> can still use bio memory after IO completion. It also ensures
> that we are not reusing the same bio on retry_rq path.
> 
> Reported-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
> Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
> ---
>   drivers/lightnvm/pblk-recovery.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
> index 009faf5db40f..3fcf062d752c 100644
> --- a/drivers/lightnvm/pblk-recovery.c
> +++ b/drivers/lightnvm/pblk-recovery.c
> @@ -376,12 +376,14 @@ static int pblk_recov_scan_oob(struct pblk *pblk, struct pblk_line *line,
>   		rq_ppas = pblk->min_write_pgs;
>   	rq_len = rq_ppas * geo->csecs;
>   
> +retry_rq:
>   	bio = bio_map_kern(dev->q, data, rq_len, GFP_KERNEL);
>   	if (IS_ERR(bio))
>   		return PTR_ERR(bio);
>   
>   	bio->bi_iter.bi_sector = 0; /* internal bio */
>   	bio_set_op_attrs(bio, REQ_OP_READ, 0);
> +	bio_get(bio);
>   
>   	rqd->bio = bio;
>   	rqd->opcode = NVM_OP_PREAD;
> @@ -394,7 +396,6 @@ static int pblk_recov_scan_oob(struct pblk *pblk, struct pblk_line *line,
>   	if (pblk_io_aligned(pblk, rq_ppas))
>   		rqd->is_seq = 1;
>   
> -retry_rq:
>   	for (i = 0; i < rqd->nr_ppas; ) {
>   		struct ppa_addr ppa;
>   		int pos;
> @@ -417,6 +418,7 @@ static int pblk_recov_scan_oob(struct pblk *pblk, struct pblk_line *line,
>   	if (ret) {
>   		pblk_err(pblk, "I/O submission failed: %d\n", ret);
>   		bio_put(bio);
> +		bio_put(bio);
>   		return ret;
>   	}
>   
> @@ -428,19 +430,25 @@ static int pblk_recov_scan_oob(struct pblk *pblk, struct pblk_line *line,
>   
>   		if (padded) {
>   			pblk_log_read_err(pblk, rqd);
> +			bio_put(bio);
>   			return -EINTR;
>   		}
>   
>   		pad_distance = pblk_pad_distance(pblk, line);
>   		ret = pblk_recov_pad_line(pblk, line, pad_distance);
> -		if (ret)
> +		if (ret) {
> +			bio_put(bio);
>   			return ret;
> +		}
>   
>   		padded = true;
> +		bio_put(bio);
>   		goto retry_rq;
>   	}
>   
>   	pblk_get_packed_meta(pblk, rqd);
> +	bio_put(bio);
> +
>   	for (i = 0; i < rqd->nr_ppas; i++) {
>   		struct pblk_sec_meta *meta = pblk_get_meta(pblk, meta_list, i);
>   		u64 lba = le64_to_cpu(meta->lba);
> 

Thanks Igor. I've merged this patch with your "lightnvm: pblk: support 
packed metadata" patch.