Re: [PATCH net v4 2/3] net: ti: icssg-prueth: Fix possible NULL pointer dereference inside emac_xmit_xdp_frame()

[Jacob Keller <jacob.e.keller@intel.com>]

On 4/15/2025 2:05 AM, Meghana Malladi wrote:
> There is an error check inside emac_xmit_xdp_frame() function which
> is called when the driver wants to transmit XDP frame, to check if
> the allocated tx descriptor is NULL, if true to exit and return
> ICSSG_XDP_CONSUMED implying failure in transmission.
> 
> In this case trying to free a descriptor which is NULL will result
> in kernel crash due to NULL pointer dereference. Fix this error handling
> and increase netdev tx_dropped stats in the caller of this function
> if the function returns ICSSG_XDP_CONSUMED.
> 
> Fixes: 62aa3246f462 ("net: ti: icssg-prueth: Add XDP support")
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/all/70d8dd76-0c76-42fc-8611-9884937c82f5@stanley.mountain/
> Signed-off-by: Meghana Malladi <m-malladi@ti.com>
> Reviewed-by: Simon Horman <horms@kernel.org>
> Reviewed-by: Roger Quadros <rogerq@kernel.org>
> ---
> 

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

> Changes from v3 (v4-v3):
> - Collected RB tag from Roger Quadros <rogerq@kernel.org>
> 
>  drivers/net/ethernet/ti/icssg/icssg_common.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
> index ec643fb69d30..b4be76e13a2f 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_common.c
> +++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
> @@ -583,7 +583,7 @@ u32 emac_xmit_xdp_frame(struct prueth_emac *emac,
>  	first_desc = k3_cppi_desc_pool_alloc(tx_chn->desc_pool);
>  	if (!first_desc) {
>  		netdev_dbg(ndev, "xdp tx: failed to allocate descriptor\n");
> -		goto drop_free_descs;	/* drop */
> +		return ICSSG_XDP_CONSUMED;	/* drop */
>  	}
>  
>  	if (page) { /* already DMA mapped by page_pool */
> @@ -671,8 +671,10 @@ static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp,
>  
>  		q_idx = smp_processor_id() % emac->tx_ch_num;
>  		result = emac_xmit_xdp_frame(emac, xdpf, page, q_idx);
> -		if (result == ICSSG_XDP_CONSUMED)
> +		if (result == ICSSG_XDP_CONSUMED) {
> +			ndev->stats.tx_dropped++;
>  			goto drop;
> +		}
>  
>  		dev_sw_netstats_rx_add(ndev, xdpf->len);
>  		return result;