Re: [dpdk-dev] [PATCH] net/octeontx2: fix corruption in segments list

[Nithin Dabilpuram <nithind1988@gmail.com>]

On Mon, Dec 21, 2020 at 07:33:08PM +0530, skori@marvell.com wrote:
> From: Sunil Kumar Kori <skori@marvell.com>
> 
> On Tx, lastseg->next is not being reset to null for multi segmented packet
> and same mbuf can be used on Rx which has a stale mbuf entry into
> mbuf->next.
> 
> On Rx, application receives mbuf with mbuf->next uninitialized though
> mbuf->nb_segs is correct. Application iterates over all segments using
> mbuf->next ignoring mbuf->nb_segs which leads to undefined behavior.
> 
> So earlier assumption of just having right value in mbuf->nb_segs is
> enough, is incorrect. Mbuf must contain valid and synced value in
> nb_segs and next pointer.
> 
> Fixes: 364eb0e46683 ("net/octeontx2: avoid per packet barrier with multi segment")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
> ---
>  drivers/net/octeontx2/otx2_rx.c | 6 ++++++
>  drivers/net/octeontx2/otx2_rx.h | 7 +++++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/octeontx2/otx2_rx.c b/drivers/net/octeontx2/otx2_rx.c
> index 2da8efe77..ffeade595 100644
> --- a/drivers/net/octeontx2/otx2_rx.c
> +++ b/drivers/net/octeontx2/otx2_rx.c
> @@ -279,6 +279,12 @@ nix_recv_pkts_vector(void *rx_queue, struct rte_mbuf **rx_pkts,
>  		vst1q_u64((uint64_t *)mbuf2->rearm_data, rearm2);
>  		vst1q_u64((uint64_t *)mbuf3->rearm_data, rearm3);
>  
> +		/* Update that no more segments */
> +		mbuf0->next = NULL;
> +		mbuf1->next = NULL;
> +		mbuf2->next = NULL;
> +		mbuf3->next = NULL;
> +
>  		/* Store the mbufs to rx_pkts */
>  		vst1q_u64((uint64_t *)&rx_pkts[packets], mbuf01);
>  		vst1q_u64((uint64_t *)&rx_pkts[packets + 2], mbuf23);
> diff --git a/drivers/net/octeontx2/otx2_rx.h b/drivers/net/octeontx2/otx2_rx.h
> index 926f614a4..0ba3d3d96 100644
> --- a/drivers/net/octeontx2/otx2_rx.h
> +++ b/drivers/net/octeontx2/otx2_rx.h
> @@ -215,6 +215,7 @@ nix_cqe_xtract_mseg(const struct nix_rx_parse_s *rx,
>  			iova_list = (const rte_iova_t *)(iova_list + 1);
>  		}
>  	}
> +	mbuf->next = NULL;
>  }
>  
>  static __rte_always_inline uint16_t
> @@ -330,10 +331,12 @@ otx2_nix_cqe_to_mbuf(const struct nix_cqe_hdr_s *cq, const uint32_t tag,
>  	*(uint64_t *)(&mbuf->rearm_data) = val;
>  	mbuf->pkt_len = len;
>  
> -	if (flag & NIX_RX_MULTI_SEG_F)
> +	if (flag & NIX_RX_MULTI_SEG_F) {
>  		nix_cqe_xtract_mseg(rx, mbuf, val);
> -	else
> +	} else {
>  		mbuf->data_len = len;
> +		mbuf->next = NULL;
> +	}
>  }
>  
>  #define CKSUM_F NIX_RX_OFFLOAD_CHECKSUM_F
> -- 
> 2.25.1
> 

Acked-by: Nithin Dabilpuram <ndabilpuram@marvell.com>