Re: [PATCH net-next 10/15] i40e: prepare for XDP metadata ops support

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [Critical] Use-After-Free in the AF_XDP Zero-Copy receive path due to stagnant index variable on error.
--

--- Patch [10]: [PATCH net-next 10/15] i40e: prepare for XDP metadata ops support ---
commit cf380b8d06da010c94723db1eb6af6df8fb0fdc8
Author: Kohei Enju <[email protected]>

i40e: prepare for XDP metadata ops support

This commit introduces struct i40e_xdp_buff to wrap an xdp_buff alongside
a pointer to an i40e_rx_desc. It passes the RX descriptor to XDP kfuncs
and adds bounds checking in the AF_XDP Zero-Copy path using
XSK_CHECK_PRIV_TYPE.

> diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
> index 9f47388eaba53..51a05ce4c7ce8 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c

[ ... ]

> @@ -472,6 +482,8 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
>  		if (i40e_is_non_eop(rx_ring, rx_desc))
>  			continue;
>  
> +		xsk_buff_to_i40e_ctx(first)->desc = rx_desc;
> +

[Severity: Critical]
This is a pre-existing issue, but does this function have a use-after-free
in its error handling path?

If xsk_buff_add_frag() fails earlier in the loop, it calls
xsk_buff_free(first) and breaks out of the loop without advancing
next_to_clean:

    if (!first)
        first = bi;
    else if (!xsk_buff_add_frag(first, bi)) {
        xsk_buff_free(first);
        break;
    }

On the subsequent NAPI poll, because next_to_process != next_to_clean,
the code loads the freed buffer pointer from the stale next_to_clean
index:

    if (next_to_process != next_to_clean)
        first = *i40e_rx_bi(rx_ring, next_to_clean);

Could this cause the next packet to be built using a freed buffer?

>  		xdp_res = i40e_run_xdp_zc(rx_ring, first, xdp_prog);
>  		i40e_handle_xdp_result_zc(rx_ring, first, rx_desc, &rx_packets,
>  					  &rx_bytes, xdp_res, &failure);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=10