Re: [PATCH v2] wifi: ath11k: fix use after free in ath11k_dp_rx_msdu_coalesce.

[Jeff Johnson <jeff.johnson@oss.qualcomm.com>]

On 5/5/2026 10:17 AM, Willmar Knikker wrote:
> In ath11k_dp_rx_msdu_coalesce the loop uses ->is_continuation after
> the dev_kfree_skb_any. This can cause a use after free kfence.
> 
> Use flag for caching is_continuation for use after the
> dev_kfree_skb_any.
> 
> Fixes: d5c65159f289 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
> Signed-off-by: Willmar Knikker <willmar@met-dubbel-l.nl>

for future reference the revision history should come after the "---"

https://www.kernel.org/doc/html/latest/process/submitting-patches.html#commentary

no need to re-submit for this; I can clean this up in my branch

> Changes in v2:
>  - add bool _is_continuation for use after the free.
>  - Add Fixes, label to commit.
> ---
>  drivers/net/wireless/ath/ath11k/dp_rx.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/dp_rx.c b/drivers/net/wireless/ath/ath11k/dp_rx.c
> index fe79109adc70..16364f76fc3c 100644
> --- a/drivers/net/wireless/ath/ath11k/dp_rx.c
> +++ b/drivers/net/wireless/ath/ath11k/dp_rx.c
> @@ -1761,6 +1761,7 @@ static int ath11k_dp_rx_msdu_coalesce(struct ath11k *ar,
>  	int buf_first_hdr_len, buf_first_len;
>  	struct hal_rx_desc *ldesc;
>  	int space_extra, rem_len, buf_len;
> +	bool is_continuation;
>  	u32 hal_rx_desc_sz = ar->ab->hw_params.hal_desc_sz;
>  
>  	/* As the msdu is spread across multiple rx buffers,
> @@ -1810,7 +1811,8 @@ static int ath11k_dp_rx_msdu_coalesce(struct ath11k *ar,
>  	rem_len = msdu_len - buf_first_len;
>  	while ((skb = __skb_dequeue(msdu_list)) != NULL && rem_len > 0) {
>  		rxcb = ATH11K_SKB_RXCB(skb);
> -		if (rxcb->is_continuation)
> +		is_continuation = rxcb->is_continuation;
> +		if (is_continuation)
>  			buf_len = DP_RX_BUFFER_SIZE - hal_rx_desc_sz;
>  		else
>  			buf_len = rem_len;
> @@ -1828,7 +1830,7 @@ static int ath11k_dp_rx_msdu_coalesce(struct ath11k *ar,
>  		dev_kfree_skb_any(skb);
>  
>  		rem_len -= buf_len;
> -		if (!rxcb->is_continuation)
> +		if (!is_continuation)
>  			break;
>  	}
>