Re: [PATCH bpf v4] xskmap: reject TX-only AF_XDP sockets

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Returning -ENOBUFS when rejecting a TX-only AF_XDP socket during map insertion is semantically incorrect and deviates from previous behavior.
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commit cc939da4429db85f32555fd19f4546a51d44ca3d
Author: Linpu Yu <linpu5433@gmail.com>

xskmap: reject TX-only AF_XDP sockets

This commit rejects TX-only AF_XDP sockets during XSKMAP updates to prevent
a kernel crash in xsk_generic_rcv(). It checks if the socket lacks an Rx
ring and returns an error before inserting it into the map.

> diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
> index afa457506274c..3bff346308d0f 100644
> --- a/net/xdp/xskmap.c
> +++ b/net/xdp/xskmap.c
> @@ -184,6 +184,10 @@ static long xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
>  	}
>  
>  	xs = (struct xdp_sock *)sock->sk;
> +	if (!READ_ONCE(xs->rx)) {
> +		sockfd_put(sock);
> +		return -ENOBUFS;

Should this return -EOPNOTSUPP or -EINVAL instead?

Earlier in this same function, -EOPNOTSUPP is returned when the socket
family is not PF_XDP. Returning -ENOBUFS might be semantically misleading
for userspace since the socket intentionally lacks an Rx ring by design,
rather than experiencing a temporary buffer shortage.

> +	}
>  
>  	map_entry = &m->xsk_map[i];
>  	node = xsk_map_node_alloc(m, map_entry);

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Sashiko AI review · https://sashiko.dev/#/patchset/20260508144344.694-1-linpu5433@gmail.com?part=1