netdev - [PATCH bpf v2 4/4] selftests/bpf: Extend bpf_iter

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Message-Id: <20260207-unix-proto-update-null-ptr-deref-v2-4-9f091330e7cd@rbox.co>
Date: Sat, 07 Feb 2026 15:34:57 +0100
From: Michal Luczaj <mhal@...x.co>
To: John Fastabend <john.fastabend@...il.com>, 
 Jakub Sitnicki <jakub@...udflare.com>, 
 Kuniyuki Iwashima <kuniyu@...gle.com>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Willem de Bruijn <willemb@...gle.com>, Cong Wang <cong.wang@...edance.com>, 
 Alexei Starovoitov <ast@...nel.org>, Yonghong Song <yhs@...com>, 
 Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Michal Luczaj <mhal@...x.co>
Subject: [PATCH bpf v2 4/4] selftests/bpf: Extend bpf_iter_unix to attempt
 deadlocking

Updating a sockmap from a unix iterator prog may lead to a deadlock.
Piggyback on the original selftest.

Signed-off-by: Michal Luczaj <mhal@...x.co>
---
 tools/testing/selftests/bpf/progs/bpf_iter_unix.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_unix.c b/tools/testing/selftests/bpf/progs/bpf_iter_unix.c
index fea275df9e22..a2652c8c3616 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter_unix.c
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_unix.c
@@ -7,6 +7,13 @@

 char _license[] SEC("license") = "GPL";

+SEC(".maps") struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} sockmap;
+
 static long sock_i_ino(const struct sock *sk)
 {
 	const struct socket *sk_socket = sk->sk_socket;
@@ -76,5 +83,8 @@ int dump_unix(struct bpf_iter__unix *ctx)

 	BPF_SEQ_PRINTF(seq, "\n");

+	/* Test for deadlock. */
+	bpf_map_update_elem(&sockmap, &(int){0}, sk, 0);
+
 	return 0;
 }

-- 
2.52.0