Re: [PATCH bpf-next 1/2] bpf, test_run: Fix user-memory-access vulnerability for LIVE_FRAMES

[KaFai Wan]

On Mon, 2026-01-05 at 11:46 +0100, Toke Høiland-Jørgensen wrote:
> KaFai Wan <kafai.wan@xxxxxxxxx> writes:
> 
> > This fix reverts to the original version and ensures data_hard_start
> > correctly points to the xdp_frame structure, eliminating the security
> > risk.
> 
> This is wrong. We should just be checking the meta_len on input to
> account for the size of xdp_frame. I'll send a patch.

Current version the actual limit of the max input meta_len for live frames is 
XDP_PACKET_HEADROOM - sizeof(struct xdp_frame), not XDP_PACKET_HEADROOM.

The original version not set xdp_buff->data_hard_start with xdp_frame, 
I set it with the correct position by adding the headroom, so there is no need 
for user to reduce the max input meta_len.

This patch is failed with the xdp_do_redirect test, I'll fix and send v2 if 
you're ok with that.
 
> 
> -Toke
> 

-- 
Thanks,
KaFai