Re: [PATCH 1/3] wifi: ath11k: fix dest ring-buffer corruption

[Baochen Qiang <quic_bqiang@quicinc.com>]

On 5/26/2025 7:48 PM, Johan Hovold wrote:
> Add the missing memory barriers to make sure that destination ring
> descriptors are read after the head pointers to avoid using stale data
> on weakly ordered architectures like aarch64.
> 
> 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@vger.kernel.org	# 5.6
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
>  drivers/net/wireless/ath/ath11k/dp_rx.c | 19 +++++++++++++++++++
>  drivers/net/wireless/ath/ath11k/dp_tx.c |  3 +++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/dp_rx.c b/drivers/net/wireless/ath/ath11k/dp_rx.c
> index ea2959305dec..dfe2d889c20f 100644
> --- a/drivers/net/wireless/ath/ath11k/dp_rx.c
> +++ b/drivers/net/wireless/ath/ath11k/dp_rx.c
> @@ -3851,6 +3851,9 @@ int ath11k_dp_process_rx_err(struct ath11k_base *ab, struct napi_struct *napi,
>  
>  	ath11k_hal_srng_access_begin(ab, srng);
>  
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>  	while (budget &&
>  	       (desc = ath11k_hal_srng_dst_get_next_entry(ab, srng))) {
>  		struct hal_reo_dest_ring *reo_desc = (struct hal_reo_dest_ring *)desc;
> @@ -4154,6 +4157,9 @@ int ath11k_dp_rx_process_wbm_err(struct ath11k_base *ab,
>  
>  	ath11k_hal_srng_access_begin(ab, srng);
>  
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>  	while (budget) {
>  		rx_desc = ath11k_hal_srng_dst_get_next_entry(ab, srng);
>  		if (!rx_desc)
> @@ -4280,6 +4286,9 @@ int ath11k_dp_process_rxdma_err(struct ath11k_base *ab, int mac_id, int budget)
>  
>  	ath11k_hal_srng_access_begin(ab, srng);
>  
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>  	while (quota-- &&
>  	       (desc = ath11k_hal_srng_dst_get_next_entry(ab, srng))) {
>  		ath11k_hal_rx_reo_ent_paddr_get(ab, desc, &paddr, &desc_bank);
> @@ -4353,6 +4362,9 @@ void ath11k_dp_process_reo_status(struct ath11k_base *ab)
>  
>  	ath11k_hal_srng_access_begin(ab, srng);
>  
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>  	while ((reo_desc = ath11k_hal_srng_dst_get_next_entry(ab, srng))) {
>  		tag = FIELD_GET(HAL_SRNG_TLV_HDR_TAG, *reo_desc);
>  
> @@ -5168,6 +5180,9 @@ static void ath11k_dp_rx_mon_dest_process(struct ath11k *ar, int mac_id,
>  	rx_bufs_used = 0;
>  	rx_mon_stats = &pmon->rx_mon_stats;
>  
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>  	while ((ring_entry = ath11k_hal_srng_dst_peek(ar->ab, mon_dst_srng))) {
>  		struct sk_buff *head_msdu, *tail_msdu;
>  
> @@ -5630,6 +5645,10 @@ static int ath11k_dp_full_mon_process_rx(struct ath11k_base *ab, int mac_id,
>  	spin_lock_bh(&mon_dst_srng->lock);
>  
>  	ath11k_hal_srng_access_begin(ar->ab, mon_dst_srng);
> +
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>  	while ((ring_entry = ath11k_hal_srng_dst_peek(ar->ab, mon_dst_srng))) {
>  		head_msdu = NULL;
>  		tail_msdu = NULL;
> diff --git a/drivers/net/wireless/ath/ath11k/dp_tx.c b/drivers/net/wireless/ath/ath11k/dp_tx.c
> index 8522c67baabf..549d17d90503 100644
> --- a/drivers/net/wireless/ath/ath11k/dp_tx.c
> +++ b/drivers/net/wireless/ath/ath11k/dp_tx.c
> @@ -700,6 +700,9 @@ void ath11k_dp_tx_completion_handler(struct ath11k_base *ab, int ring_id)
>  
>  	ath11k_hal_srng_access_begin(ab, status_ring);
>  
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>  	while ((ATH11K_TX_COMPL_NEXT(tx_ring->tx_status_head) !=
>  		tx_ring->tx_status_tail) &&
>  	       (desc = ath11k_hal_srng_dst_get_next_entry(ab, status_ring))) {

Johan, dma_rmb() is put inside _srng_access_begin() for ath12k, but here inside each
caller. Can we achieve consistency between two drivers?