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xskmap: reject TX-only AF_XDP sockets

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XSKMAP entries are used as redirect targets for incoming XDP frames.
A TX-only AF_XDP socket lacks an Rx ring and cannot handle redirected
traffic, but xsk_map_update_elem() currently allows such sockets to
be inserted into the map.

Redirecting packets to such a socket on the veth generic-XDP path
causes a kernel crash in xsk_generic_rcv().

This became possible after xsk_is_setup_for_bpf_map() was removed from
the XSKMAP update path, which allowed bound TX-only sockets to be
inserted into the map.

Reject TX-only sockets during XSKMAP updates to avoid the crash.
They remain fully operational for pure Tx purposes outside XSKMAP.

Fixes: 968be23cea ("xsk: Fix possible segfault at xskmap entry insertion")
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Yifan Wu <yifanwucs@gmail.com>
Signed-off-by: Linpu Yu <linpu5433@gmail.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://lore.kernel.org/r/20260508144344.694-1-linpu5433@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Linpu Yu 2026-05-08 22:43:43 +08:00 committed by Alexei Starovoitov
parent 512809bb8a
commit bf6d507f7e
1 changed files with 4 additions and 0 deletions
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4
net/xdp/xskmap.c
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@ -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;
}
map_entry = &m->xsk_map[i];
node = xsk_map_node_alloc(m, map_entry);