Re: [PATCH v3 4/4] wifi: ath12k: fix dest ring-buffer corruption when ring is full

Baochen Qiang
2025-06-25T01:54:49Z

On 6/17/2025 4:44 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: WCN7850 hw2.0 WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
>
> Fixes: d889913205cf ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
> Cc: stable@vger.kernel.org # 6.3
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
> drivers/net/wireless/ath/ath12k/hal.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath12k/hal.c b/drivers/net/wireless/ath/ath12k/hal.c
> index d8193d9577bb..6406fcf5d69f 100644
> --- a/drivers/net/wireless/ath/ath12k/hal.c
> +++ b/drivers/net/wireless/ath/ath12k/hal.c
> @@ -2170,7 +2170,6 @@ void ath12k_hal_srng_access_end(struct ath12k_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
> @@ -2185,7 +2184,11 @@ void ath12k_hal_srng_access_end(struct ath12k_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) {
> @@ -2201,6 +2204,10 @@ void ath12k_hal_srng_access_end(struct ath12k_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();
> ath12k_hif_write32(ab,
> (unsigned long)srng->u.dst_ring.tp_addr -
> (unsigned long)ab->mem,

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