Re: [PATCH] net: wwan: iosm: fix potential skb leak in MUX DL decode

[Loic Poulain]

Hi Fang,

On Mon, Nov 2, 2026 at 9:19 AM Fang Xieyan <fangxy@xxxxxxxxxxxx> wrote:
>
> ipc_mux_dl_decode() owns the received skb and frees it after
> decoding. However, the early return when skb->data is NULL
> bypasses the skb cleanup.
>
> Free the skb through ipc_pcie_kfree_skb() before returning
> to ensure that both the DMA mapping and skb are released.
>
> Fixes: 3670970dd8c6 ("net: iosm: shared memory IPC interface")
> Reviewed-by: Guanglei Zhu <zhugl3@xxxxxxxxxxxx>
> Signed-off-by: Fang Xieyan <fangxy@xxxxxxxxxxxx>
> ---
>  drivers/net/wwan/iosm/iosm_ipc_mux_codec.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c b/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c
> index 0bbd41263cc2..61700688eac9 100644
> --- a/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c
> +++ b/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c
> @@ -693,8 +693,10 @@ void ipc_mux_dl_decode(struct iosm_mux *ipc_mux, struct sk_buff *skb)
>  {
>         u32 signature;
>
> -       if (!skb->data)
> +       if (!skb->data) {

Can skb->data ever be NULL in the first place? This looks rather
unusual. If it can happen, please describe what leads to that
situation. Otherwise, the check should simply be removed.

> +               ipc_pcie_kfree_skb(ipc_mux->pcie, skb);
>                 return;
> +       }
>
>         /* Decode the MUX header type. */
>         signature = le32_to_cpup((__le32 *)skb->data);
> --
> 2.50.1
>