[PATCH bpf-next v4 3/3] selftests/bpf: xdp: test dev_xdp_install() rejects device-bound program
From: Jiayuan Chen <jiayuan.chen@linux.dev>
Date: 2026-08-10 05:07:56
Also in:
bpf, linux-kselftest, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest, xdp (express data path) · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Shuah Khan, Linus Torvalds, David S. Miller, Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend
bpf_xdp_link_update() used to skip the checks in dev_xdp_attach(). Add a test that makes a generic XDP link with a normal program and then tries to swap in a device-bound program, which must fail. Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev> --- .../bpf/prog_tests/xdp_dev_bound_only.c | 49 +++++++++++++++++++ 1 file changed, 49 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_dev_bound_only.c b/tools/testing/selftests/bpf/prog_tests/xdp_dev_bound_only.c
index 7dd18c6d06c6..4a13f8ec4300 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_dev_bound_only.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_dev_bound_only.c@@ -1,9 +1,11 @@ // SPDX-License-Identifier: GPL-2.0 #include <net/if.h> +#include <linux/if_link.h> #include <test_progs.h> #include <network_helpers.h> #define LOCAL_NETNS "xdp_dev_bound_only_netns" +#define LINK_UPDATE_NETNS "xdp_dev_bound_only_lu_netns" static int load_dummy_prog(char *name, __u32 ifindex, __u32 flags) {
@@ -59,3 +61,50 @@ void test_xdp_dev_bound_only_offdev(void) */ SYS_NOFAIL("ip netns del " LOCAL_NETNS); } + +/* A device-bound program must not run on the XDP software path. + * dev_xdp_attach() rejected such programs, but bpf_xdp_link_update() reaches + * dev_xdp_install() directly and bypasses it, so the check has to live in + * dev_xdp_install(). Create a generic (SKB) XDP link with a normal program, + * then try to swap in a device-bound program via BPF_LINK_UPDATE. + */ +void test_xdp_dev_bound_only_link_update(void) +{ + LIBBPF_OPTS(bpf_link_create_opts, lopts, .flags = XDP_FLAGS_SKB_MODE); + int base_fd = -1, devbound_fd = -1, link_fd = -1; + struct nstoken *tok = NULL; + __u32 ifindex; + int err; + + SYS(out, "ip netns add " LINK_UPDATE_NETNS); + tok = open_netns(LINK_UPDATE_NETNS); + if (!ASSERT_OK_PTR(tok, "open_netns")) + goto out; + + SYS(out, "ip link add eth42 type veth"); + ifindex = if_nametoindex("eth42"); + if (!ASSERT_NEQ(ifindex, 0, "if_nametoindex")) + goto out; + + devbound_fd = load_dummy_prog("devbound", ifindex, BPF_F_XDP_DEV_BOUND_ONLY); + if (!ASSERT_GE(devbound_fd, 0, "load_dummy_prog devbound")) + goto out; + + base_fd = load_dummy_prog("base", 0, 0); + if (!ASSERT_GE(base_fd, 0, "load_dummy_prog base")) + goto out; + + link_fd = bpf_link_create(base_fd, ifindex, BPF_XDP, &lopts); + if (!ASSERT_GE(link_fd, 0, "bpf_link_create")) + goto out; + + err = bpf_link_update(link_fd, devbound_fd, NULL); + ASSERT_EQ(err, -EINVAL, "link_update device-bound rejected"); + +out: + close(link_fd); + close(base_fd); + close(devbound_fd); + close_netns(tok); + SYS_NOFAIL("ip netns del " LINK_UPDATE_NETNS); +}
--
2.43.0