[PATCH v2 5/5] wifi: ath11k: fix dest ring-buffer corruption when ring is full

[Baochen Qiang]

On 6/4/2025 10:34 PM, Johan Hovold wrote:
> Add the missing memory barriers to make sure that destination ring
> descriptors are read before updating the tail pointer (and passing
> ownership to the device) to avoid memory corruption on weakly ordered
> architectures like aarch64 when the ring is full.
> 
> Tested-on: WCN6855 hw2.1 WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.41
> 
> Fixes: d5c65159f289 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
> Cc: stable at vger.kernel.org      # 5.6
> Signed-off-by: Johan Hovold <johan+linaro at kernel.org>
> ---
>  drivers/net/wireless/ath/ath11k/hal.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
> index 927ed2bc3fbf..7eeffb36899e 100644
> --- a/drivers/net/wireless/ath/ath11k/hal.c
> +++ b/drivers/net/wireless/ath/ath11k/hal.c
> @@ -854,7 +854,6 @@ void ath11k_hal_srng_access_end(struct ath11k_base *ab, struct hal_srng *srng)
>  {
>  	lockdep_assert_held(&srng->lock);
>  
> -	/* TODO: See if we need a write memory barrier here */
>  	if (srng->flags & HAL_SRNG_FLAGS_LMAC_RING) {
>  		/* For LMAC rings, ring pointer updates are done through FW and
>  		 * hence written to a shared memory location that is read by FW
> @@ -869,7 +868,11 @@ void ath11k_hal_srng_access_end(struct ath11k_base *ab, struct hal_srng *srng)
>  			WRITE_ONCE(*srng->u.src_ring.hp_addr, srng->u.src_ring.hp);
>  		} else {
>  			srng->u.dst_ring.last_hp = *srng->u.dst_ring.hp_addr;
> -			*srng->u.dst_ring.tp_addr = srng->u.dst_ring.tp;
> +			/* Make sure descriptor is read before updating the
> +			 * tail pointer.
> +			 */
> +			dma_mb();
> +			WRITE_ONCE(*srng->u.dst_ring.tp_addr, srng->u.dst_ring.tp);
>  		}
>  	} else {
>  		if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
> @@ -885,6 +888,10 @@ void ath11k_hal_srng_access_end(struct ath11k_base *ab, struct hal_srng *srng)
>  					   srng->u.src_ring.hp);
>  		} else {
>  			srng->u.dst_ring.last_hp = *srng->u.dst_ring.hp_addr;
> +			/* Make sure descriptor is read before updating the
> +			 * tail pointer.
> +			 */
> +			mb();
>  			ath11k_hif_write32(ab,
>  					   (unsigned long)srng->u.dst_ring.tp_addr -
>  					   (unsigned long)ab->mem,

Reviewed-by: Baochen Qiang <quic_bqiang at quicinc.com>