On Thu, Jun 15, 2023 at 11:45:36AM +0200, Simon Horman wrote:
Hi Simon,
> In igc_clean_rx_irq() the result of a call to igc_xdp_run_prog() is assigned
> to the skb local variable. This may be an ERR_PTR.
>
> A little later the following is executed, which seems to be a
> possible dereference of an ERR_PTR.
>
> total_bytes += skb->len;
>
> Avoid this problem by continuing the loop in which all of the
> above occurs once the handling of the NULL case completes.
>
> This proposed fix is speculative - I do not have deep knowledge of this
> driver. And I am concerned about the effect of skipping the following
> logic:
>
> igc_put_rx_buffer(rx_ring, rx_buffer, rx_buffer_pgcnt);
> cleaned_count++;
this will break - you have to recycle the buffer to have it going.
>
> Flagged by Smatch as:
>
> .../igc_main.c:2467 igc_xdp_run_prog() warn: passing zero to 'ERR_PTR'
how about PTR_ERR_OR_ZERO() ? this would silence smatch and is not an
intrusive change. another way is to get rid of ERR_PTR() around skb/xdp
run result but i think the former would be just fine.
>
> Compile tested only.
>
> Fixes: 26575105d6ed ("igc: Add initial XDP support")
> Signed-off-by: Simon Horman <horms@xxxxxxxxxx>
> ---
> drivers/net/ethernet/intel/igc/igc_main.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 88145c30c919..b58c8a674bd1 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -2586,6 +2586,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
>
> total_packets++;
> total_bytes += size;
> + continue;
> } else if (skb)
> igc_add_rx_frag(rx_ring, rx_buffer, skb, size);
> else if (ring_uses_build_skb(rx_ring))
>
>
