Users of the Lenovo ThinkPad X13s have reported that Wi-Fi sometimes
breaks and the log fills up with errors like:

    ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1484, expected 1492
    ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484

which based on a quick look at the driver seemed to indicate some kind
of ring-buffer corruption.

Miaoqing Pan tracked it down to the host seeing the updated destination
ring head pointer before the updated descriptor, and the error handling
for that in turn leaves the ring buffer in an inconsistent state.

Add the missing memory barrier to make sure that the descriptor is read
after the head pointer to address the root cause of the corruption while
fixing up the error handling in case there are ever any (ordering) bugs
on the device side.

Note that the READ_ONCE() are only needed to avoid compiler mischief in
case the ring-buffer helpers are ever inlined.

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")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
Link: https://lore.kernel.org/20250310010217.3845141-3-quic_miaoqing@quicinc.com
Cc: Miaoqing Pan <quic_miaoqing@quicinc.com>
Cc: stable@vger.kernel.org	# 5.6
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
---
 drivers/net/wireless/ath/ath11k/ce.c  | 11 +++++------
 drivers/net/wireless/ath/ath11k/hal.c |  4 ++--
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/ce.c b/drivers/net/wireless/ath/ath11k/ce.c
index e66e86bdec20..9d8efec46508 100644
--- a/drivers/net/wireless/ath/ath11k/ce.c
+++ b/drivers/net/wireless/ath/ath11k/ce.c
@@ -393,11 +393,10 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe,
 		goto err;
 	}
 
+	/* Make sure descriptor is read after the head pointer. */
+	dma_rmb();
+
 	*nbytes = ath11k_hal_ce_dst_status_get_length(desc);
-	if (*nbytes == 0) {
-		ret = -EIO;
-		goto err;
-	}
 
 	*skb = pipe->dest_ring->skb[sw_index];
 	pipe->dest_ring->skb[sw_index] = NULL;
@@ -430,8 +429,8 @@ static void ath11k_ce_recv_process_cb(struct ath11k_ce_pipe *pipe)
 		dma_unmap_single(ab->dev, ATH11K_SKB_RXCB(skb)->paddr,
 				 max_nbytes, DMA_FROM_DEVICE);
 
-		if (unlikely(max_nbytes < nbytes)) {
-			ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)",
+		if (unlikely(max_nbytes < nbytes || nbytes == 0)) {
+			ath11k_warn(ab, "unexpected rx length (nbytes %d, max %d)",
 				    nbytes, max_nbytes);
 			dev_kfree_skb_any(skb);
 			continue;
diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
index 61f4b6dd5380..8cb1505a5a0c 100644
--- a/drivers/net/wireless/ath/ath11k/hal.c
+++ b/drivers/net/wireless/ath/ath11k/hal.c
@@ -599,7 +599,7 @@ u32 ath11k_hal_ce_dst_status_get_length(void *buf)
 	struct hal_ce_srng_dst_status_desc *desc = buf;
 	u32 len;
 
-	len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, desc->flags);
+	len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, READ_ONCE(desc->flags));
 	desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN;
 
 	return len;
@@ -829,7 +829,7 @@ void ath11k_hal_srng_access_begin(struct ath11k_base *ab, struct hal_srng *srng)
 		srng->u.src_ring.cached_tp =
 			*(volatile u32 *)srng->u.src_ring.tp_addr;
 	} else {
-		srng->u.dst_ring.cached_hp = *srng->u.dst_ring.hp_addr;
+		srng->u.dst_ring.cached_hp = READ_ONCE(*srng->u.dst_ring.hp_addr);
 
 		/* Try to prefetch the next descriptor in the ring */
 		if (srng->flags & HAL_SRNG_FLAGS_CACHED)
-- 
2.48.1

On Fri, 21 Mar 2025 10:49:16 +0100, Johan Hovold wrote:
> Users of the Lenovo ThinkPad X13s have reported that Wi-Fi sometimes
> breaks and the log fills up with errors like:
> 
>     ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1484, expected 1492
>     ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
> 
> which based on a quick look at the driver seemed to indicate some kind
> of ring-buffer corruption.
> 
> [...]

Applied, thanks!

[1/1] wifi: ath11k: fix ring-buffer corruption
      commit: 6d037a372f817e9fcb56482f37917545596bd776

Best regards,
-- 
Jeff Johnson <jeff.johnson@oss.qualcomm.com>

On 3/21/2025 5:49 PM, Johan Hovold wrote:
> Users of the Lenovo ThinkPad X13s have reported that Wi-Fi sometimes
> breaks and the log fills up with errors like:
> 
>      ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1484, expected 1492
>      ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
> 
> which based on a quick look at the driver seemed to indicate some kind
> of ring-buffer corruption.
> 
> Miaoqing Pan tracked it down to the host seeing the updated destination
> ring head pointer before the updated descriptor, and the error handling
> for that in turn leaves the ring buffer in an inconsistent state.
> 
> Add the missing memory barrier to make sure that the descriptor is read
> after the head pointer to address the root cause of the corruption while
> fixing up the error handling in case there are ever any (ordering) bugs
> on the device side.
> 
> Note that the READ_ONCE() are only needed to avoid compiler mischief in
> case the ring-buffer helpers are ever inlined.
> 
> 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")
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
> Link: https://lore.kernel.org/20250310010217.3845141-3-quic_miaoqing@quicinc.com
> Cc: Miaoqing Pan <quic_miaoqing@quicinc.com>
> Cc: stable@vger.kernel.org	# 5.6
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
>   drivers/net/wireless/ath/ath11k/ce.c  | 11 +++++------
>   drivers/net/wireless/ath/ath11k/hal.c |  4 ++--
>   2 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/ce.c b/drivers/net/wireless/ath/ath11k/ce.c
> index e66e86bdec20..9d8efec46508 100644
> --- a/drivers/net/wireless/ath/ath11k/ce.c
> +++ b/drivers/net/wireless/ath/ath11k/ce.c
> @@ -393,11 +393,10 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe,
>   		goto err;
>   	}
>   
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>   	*nbytes = ath11k_hal_ce_dst_status_get_length(desc);
> -	if (*nbytes == 0) {
> -		ret = -EIO;
> -		goto err;
> -	}
>   
>   	*skb = pipe->dest_ring->skb[sw_index];
>   	pipe->dest_ring->skb[sw_index] = NULL;
> @@ -430,8 +429,8 @@ static void ath11k_ce_recv_process_cb(struct ath11k_ce_pipe *pipe)
>   		dma_unmap_single(ab->dev, ATH11K_SKB_RXCB(skb)->paddr,
>   				 max_nbytes, DMA_FROM_DEVICE);
>   
> -		if (unlikely(max_nbytes < nbytes)) {
> -			ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)",
> +		if (unlikely(max_nbytes < nbytes || nbytes == 0)) {
> +			ath11k_warn(ab, "unexpected rx length (nbytes %d, max %d)",
>   				    nbytes, max_nbytes);
>   			dev_kfree_skb_any(skb);
>   			continue;
> diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
> index 61f4b6dd5380..8cb1505a5a0c 100644
> --- a/drivers/net/wireless/ath/ath11k/hal.c
> +++ b/drivers/net/wireless/ath/ath11k/hal.c
> @@ -599,7 +599,7 @@ u32 ath11k_hal_ce_dst_status_get_length(void *buf)
>   	struct hal_ce_srng_dst_status_desc *desc = buf;
>   	u32 len;
>   
> -	len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, desc->flags);
> +	len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, READ_ONCE(desc->flags));
>   	desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN;
>   
>   	return len;
> @@ -829,7 +829,7 @@ void ath11k_hal_srng_access_begin(struct ath11k_base *ab, struct hal_srng *srng)
>   		srng->u.src_ring.cached_tp =
>   			*(volatile u32 *)srng->u.src_ring.tp_addr;
>   	} else {
> -		srng->u.dst_ring.cached_hp = *srng->u.dst_ring.hp_addr;
> +		srng->u.dst_ring.cached_hp = READ_ONCE(*srng->u.dst_ring.hp_addr);
>   
>   		/* Try to prefetch the next descriptor in the ring */
>   		if (srng->flags & HAL_SRNG_FLAGS_CACHED)

Reviewed-by: Miaoqing Pan <quic_miaoqing@quicinc.com>

Hi Jeff,

On Fri, Mar 21, 2025 at 10:49:16AM +0100, Johan Hovold wrote:
> Users of the Lenovo ThinkPad X13s have reported that Wi-Fi sometimes
> breaks and the log fills up with errors like:
> 
>     ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1484, expected 1492
>     ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
> 
> which based on a quick look at the driver seemed to indicate some kind
> of ring-buffer corruption.
> 
> Miaoqing Pan tracked it down to the host seeing the updated destination
> ring head pointer before the updated descriptor, and the error handling
> for that in turn leaves the ring buffer in an inconsistent state.
> 
> Add the missing memory barrier to make sure that the descriptor is read
> after the head pointer to address the root cause of the corruption while
> fixing up the error handling in case there are ever any (ordering) bugs
> on the device side.
> 
> Note that the READ_ONCE() are only needed to avoid compiler mischief in
> case the ring-buffer helpers are ever inlined.
> 
> 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")
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
> Link: https://lore.kernel.org/20250310010217.3845141-3-quic_miaoqing@quicinc.com
> Cc: Miaoqing Pan <quic_miaoqing@quicinc.com>
> Cc: stable@vger.kernel.org	# 5.6
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>

This patch fixes a long-standing issue that is hurting user of machines
like the X13s, but as far as I can tell it has not been picked up yet
(perhaps due to the temporary MAINTAINERS glitch that caused the
wireless list not to be CCed?).

Would be good to get this fixed in 6.15 and backported to stable.

The following related patches are also not yet in linux-next:

	https://lore.kernel.org/lkml/20250321145302.4775-1-johan+linaro@kernel.org/
	https://lore.kernel.org/lkml/20250321095219.19369-1-johan+linaro@kernel.org/

Note that I still intend to sending follow-on fixes for the other
missing barriers, but I'm a bit short on time at the moment.

Johan

Hi Johan,

On Fri, Mar 21, 2025 at 4:51 AM Johan Hovold <johan+linaro@kernel.org> wrote:
>
> Users of the Lenovo ThinkPad X13s have reported that Wi-Fi sometimes
> breaks and the log fills up with errors like:
>
>     ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1484, expected 1492
>     ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
>
> which based on a quick look at the driver seemed to indicate some kind
> of ring-buffer corruption.
>
> Miaoqing Pan tracked it down to the host seeing the updated destination
> ring head pointer before the updated descriptor, and the error handling
> for that in turn leaves the ring buffer in an inconsistent state.
>
> Add the missing memory barrier to make sure that the descriptor is read
> after the head pointer to address the root cause of the corruption while
> fixing up the error handling in case there are ever any (ordering) bugs
> on the device side.
>
> Note that the READ_ONCE() are only needed to avoid compiler mischief in
> case the ring-buffer helpers are ever inlined.
>
> 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")
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
> Link: https://lore.kernel.org/20250310010217.3845141-3-quic_miaoqing@quicinc.com
> Cc: Miaoqing Pan <quic_miaoqing@quicinc.com>
> Cc: stable@vger.kernel.org      # 5.6
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
>  drivers/net/wireless/ath/ath11k/ce.c  | 11 +++++------
>  drivers/net/wireless/ath/ath11k/hal.c |  4 ++--
>  2 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath11k/ce.c b/drivers/net/wireless/ath/ath11k/ce.c
> index e66e86bdec20..9d8efec46508 100644
> --- a/drivers/net/wireless/ath/ath11k/ce.c
> +++ b/drivers/net/wireless/ath/ath11k/ce.c
> @@ -393,11 +393,10 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe,
>                 goto err;
>         }
>
> +       /* Make sure descriptor is read after the head pointer. */
> +       dma_rmb();
> +
>         *nbytes = ath11k_hal_ce_dst_status_get_length(desc);
> -       if (*nbytes == 0) {
> -               ret = -EIO;
> -               goto err;
> -       }
>
>         *skb = pipe->dest_ring->skb[sw_index];
>         pipe->dest_ring->skb[sw_index] = NULL;
> @@ -430,8 +429,8 @@ static void ath11k_ce_recv_process_cb(struct ath11k_ce_pipe *pipe)
>                 dma_unmap_single(ab->dev, ATH11K_SKB_RXCB(skb)->paddr,
>                                  max_nbytes, DMA_FROM_DEVICE);
>
> -               if (unlikely(max_nbytes < nbytes)) {
> -                       ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)",
> +               if (unlikely(max_nbytes < nbytes || nbytes == 0)) {
> +                       ath11k_warn(ab, "unexpected rx length (nbytes %d, max %d)",
>                                     nbytes, max_nbytes);
>                         dev_kfree_skb_any(skb);
>                         continue;
> diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
> index 61f4b6dd5380..8cb1505a5a0c 100644
> --- a/drivers/net/wireless/ath/ath11k/hal.c
> +++ b/drivers/net/wireless/ath/ath11k/hal.c
> @@ -599,7 +599,7 @@ u32 ath11k_hal_ce_dst_status_get_length(void *buf)
>         struct hal_ce_srng_dst_status_desc *desc = buf;
>         u32 len;
>
> -       len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, desc->flags);
> +       len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, READ_ONCE(desc->flags));
>         desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN;
>
>         return len;
> @@ -829,7 +829,7 @@ void ath11k_hal_srng_access_begin(struct ath11k_base *ab, struct hal_srng *srng)
>                 srng->u.src_ring.cached_tp =
>                         *(volatile u32 *)srng->u.src_ring.tp_addr;
>         } else {
> -               srng->u.dst_ring.cached_hp = *srng->u.dst_ring.hp_addr;
> +               srng->u.dst_ring.cached_hp = READ_ONCE(*srng->u.dst_ring.hp_addr);
>
>                 /* Try to prefetch the next descriptor in the ring */
>                 if (srng->flags & HAL_SRNG_FLAGS_CACHED)
> --
> 2.48.1
>

Like the others, I was seeing this message multiple times a day, and
on a not so rare occasion it would also take the wifi device offline,
with this patch applied, I do not see that at all here.

Tested-by: Steev Klimaszewski <steev@kali.org>

On 3/21/25 10:49, Johan Hovold wrote:
> Users of the Lenovo ThinkPad X13s have reported that Wi-Fi sometimes
> breaks and the log fills up with errors like:
>
>      ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1484, expected 1492
>      ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
>
> which based on a quick look at the driver seemed to indicate some kind
> of ring-buffer corruption.
>
I had this issue on the Windows Dev Kit 2023 and X13s, interestingly
never on the HP Omnibook X14. With this patch there have been no
occurrences.

Tested-by: Jens Glathe <jens.glathe@oldschoolsolutions.biz>

with best regards

Jens

On 3/21/25 02:49, Johan Hovold wrote:
> Users of the Lenovo ThinkPad X13s have reported that Wi-Fi sometimes
> breaks and the log fills up with errors like:
> 
>      ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1484, expected 1492
>      ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
> 
> which based on a quick look at the driver seemed to indicate some kind
> of ring-buffer corruption.
> 
> Miaoqing Pan tracked it down to the host seeing the updated destination
> ring head pointer before the updated descriptor, and the error handling
> for that in turn leaves the ring buffer in an inconsistent state.
> 
> Add the missing memory barrier to make sure that the descriptor is read
> after the head pointer to address the root cause of the corruption while
> fixing up the error handling in case there are ever any (ordering) bugs
> on the device side.
> 
> Note that the READ_ONCE() are only needed to avoid compiler mischief in
> case the ring-buffer helpers are ever inlined.
> 
> 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")
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
> Link: https://lore.kernel.org/20250310010217.3845141-3-quic_miaoqing@quicinc.com
> Cc: Miaoqing Pan <quic_miaoqing@quicinc.com>
> Cc: stable@vger.kernel.org	# 5.6
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
>   drivers/net/wireless/ath/ath11k/ce.c  | 11 +++++------
>   drivers/net/wireless/ath/ath11k/hal.c |  4 ++--
>   2 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/ce.c b/drivers/net/wireless/ath/ath11k/ce.c
> index e66e86bdec20..9d8efec46508 100644
> --- a/drivers/net/wireless/ath/ath11k/ce.c
> +++ b/drivers/net/wireless/ath/ath11k/ce.c
> @@ -393,11 +393,10 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe,
>   		goto err;
>   	}
>   
> +	/* Make sure descriptor is read after the head pointer. */
> +	dma_rmb();
> +
>   	*nbytes = ath11k_hal_ce_dst_status_get_length(desc);
> -	if (*nbytes == 0) {
> -		ret = -EIO;
> -		goto err;
> -	}
>   
>   	*skb = pipe->dest_ring->skb[sw_index];
>   	pipe->dest_ring->skb[sw_index] = NULL;
> @@ -430,8 +429,8 @@ static void ath11k_ce_recv_process_cb(struct ath11k_ce_pipe *pipe)
>   		dma_unmap_single(ab->dev, ATH11K_SKB_RXCB(skb)->paddr,
>   				 max_nbytes, DMA_FROM_DEVICE);
>   
> -		if (unlikely(max_nbytes < nbytes)) {
> -			ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)",
> +		if (unlikely(max_nbytes < nbytes || nbytes == 0)) {
> +			ath11k_warn(ab, "unexpected rx length (nbytes %d, max %d)",
>   				    nbytes, max_nbytes);
>   			dev_kfree_skb_any(skb);
>   			continue;
> diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
> index 61f4b6dd5380..8cb1505a5a0c 100644
> --- a/drivers/net/wireless/ath/ath11k/hal.c
> +++ b/drivers/net/wireless/ath/ath11k/hal.c
> @@ -599,7 +599,7 @@ u32 ath11k_hal_ce_dst_status_get_length(void *buf)
>   	struct hal_ce_srng_dst_status_desc *desc = buf;
>   	u32 len;
>   
> -	len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, desc->flags);
> +	len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, READ_ONCE(desc->flags));
>   	desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN;
>   
>   	return len;
> @@ -829,7 +829,7 @@ void ath11k_hal_srng_access_begin(struct ath11k_base *ab, struct hal_srng *srng)
>   		srng->u.src_ring.cached_tp =
>   			*(volatile u32 *)srng->u.src_ring.tp_addr;
>   	} else {
> -		srng->u.dst_ring.cached_hp = *srng->u.dst_ring.hp_addr;
> +		srng->u.dst_ring.cached_hp = READ_ONCE(*srng->u.dst_ring.hp_addr);
>   
>   		/* Try to prefetch the next descriptor in the ring */
>   		if (srng->flags & HAL_SRNG_FLAGS_CACHED)

I was experiencing this issue several times per day, but haven't hit it 
once in the last few days while testing this patch.

Tested-by: Clayton Craft <clayton@craftyguy.net>