Merge branch 'bpf-sockmap-fix-af_unix-null-ptr-deref-in-proto-update'

Michal Luczaj says:

====================
bpf, sockmap: Fix af_unix null-ptr-deref in proto update

Updating sockmap/sockhash using a unix sock races unix_stream_connect():
when sock_map_sk_state_allowed() passes (sk_state == TCP_ESTABLISHED),
unix_peer(sk) in unix_stream_bpf_update_proto() may still return NULL.
====================

Link: https://patch.msgid.link/20260414-unix-proto-update-null-ptr-deref-v4-0-2af6fe97918e@rbox.co
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Author: Martin KaFai Lau

net/core/sock_map.c

@@ -530,7 +530,7 @@ static bool sock_map_redirect_allowed(const struct sock *sk)
 	if (sk_is_tcp(sk))
 		return sk->sk_state != TCP_LISTEN;
 	else
-		return sk->sk_state == TCP_ESTABLISHED;
+		return READ_ONCE(sk->sk_state) == TCP_ESTABLISHED;
 }
 
 static bool sock_map_sk_is_suitable(const struct sock *sk)
@@ -543,7 +543,7 @@ static bool sock_map_sk_state_allowed(const struct sock *sk)
 	if (sk_is_tcp(sk))
 		return (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_LISTEN);
 	if (sk_is_stream_unix(sk))
-		return (1 << sk->sk_state) & TCPF_ESTABLISHED;
+		return (1 << READ_ONCE(sk->sk_state)) & TCPF_ESTABLISHED;
 	if (sk_is_vsock(sk) &&
 	    (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET))
 		return (1 << sk->sk_state) & TCPF_ESTABLISHED;

net/unix/af_unix.c

@@ -3735,15 +3735,15 @@ static int bpf_iter_unix_seq_show(struct seq_file *seq, void *v)
 	struct bpf_prog *prog;
 	struct sock *sk = v;
 	uid_t uid;
-	bool slow;
 	int ret;
 
 	if (v == SEQ_START_TOKEN)
 		return 0;
 
-	slow = lock_sock_fast(sk);
+	lock_sock(sk);
+	unix_state_lock(sk);
 
-	if (unlikely(sk_unhashed(sk))) {
+	if (unlikely(sock_flag(sk, SOCK_DEAD))) {
 		ret = SEQ_SKIP;
 		goto unlock;
 	}
@@ -3753,7 +3753,8 @@ static int bpf_iter_unix_seq_show(struct seq_file *seq, void *v)
 	prog = bpf_iter_get_info(&meta, false);
 	ret = unix_prog_seq_show(prog, &meta, v, uid);
 unlock:
-	unlock_sock_fast(sk, slow);
+	unix_state_unlock(sk);
+	release_sock(sk);
 	return ret;
 }
 

net/unix/unix_bpf.c

@@ -185,6 +185,9 @@ int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool r
 	 */
 	if (!psock->sk_pair) {
 		sk_pair = unix_peer(sk);
+		if (unlikely(!sk_pair))
+			return -EINVAL;
+
 		sock_hold(sk_pair);
 		psock->sk_pair = sk_pair;
 	}

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;
 }