Subject: Re: [PATCH bpf-next v2] bpf: Allow XDP dev-bound programs to perform XDP_REDIRECT into maps

From: Martin KaFai Lau <[email-masked]>
Date: Wed, 23 Apr 2025 15:29:53 -0700

On 4/23/25 10:44 AM, Lorenzo Bianconi wrote:
> In the current implementation if the program is dev-bound to a specific
> device, it will not be possible to perform XDP_REDIRECT into a DEVMAP
> or CPUMAP even if the program is running in the driver NAPI context and
> it is not attached to any map entry. This seems in contrast with the
> explanation available in bpf_prog_map_compatible routine.
> Fix the issue introducing __bpf_prog_map_compatible utility routine in
> order to avoid bpf_prog_is_dev_bound() check running bpf_check_tail_call()
> at program load time (bpf_prog_select_runtime()).
> Continue forbidding to attach a dev-bound program to XDP maps
> (BPF_MAP_TYPE_PROG_ARRAY, BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_CPUMAP).
> 
> Fixes: 3d76a4d3d4e59 ("bpf: XDP metadata RX kfuncs")
> Signed-off-by: Lorenzo Bianconi <[email-masked]>
> ---
> Changes in v2:
> - Introduce __bpf_prog_map_compatible() utility routine in order to skip
>    bpf_prog_is_dev_bound check in bpf_check_tail_call()
> - Extend xdp_metadata selftest
> - Link to v1: https://lore.kernel.org/r/[email-masked]
> ---
>   kernel/bpf/core.c                                  | 27 +++++++++++++---------
>   .../selftests/bpf/prog_tests/xdp_metadata.c        | 22 +++++++++++++++++-
>   tools/testing/selftests/bpf/progs/xdp_metadata.c   | 13 +++++++++++

The change lgtm. Please separate the selftest changes to patch 2. Thanks.

pw-bot: cr