Patch "af_unix: Disable MSG_OOB handling for sockets in sockmap/sockhash" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    af_unix: Disable MSG_OOB handling for sockets in sockmap/sockhash

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     af_unix-disable-msg_oob-handling-for-sockets-in-sock.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 04920f7f4d32a3ebc08b0dd55db430f0bfacba09
Author: Michal Luczaj <mhal@xxxxxxx>
Date:   Sat Jul 13 21:41:38 2024 +0200

    af_unix: Disable MSG_OOB handling for sockets in sockmap/sockhash
    
    [ Upstream commit 638f32604385fd23059985da8de918e9c18f0b98 ]
    
    AF_UNIX socket tracks the most recent OOB packet (in its receive queue)
    with an `oob_skb` pointer. BPF redirecting does not account for that: when
    an OOB packet is moved between sockets, `oob_skb` is left outdated. This
    results in a single skb that may be accessed from two different sockets.
    
    Take the easy way out: silently drop MSG_OOB data targeting any socket that
    is in a sockmap or a sockhash. Note that such silent drop is akin to the
    fate of redirected skb's scm_fp_list (SCM_RIGHTS, SCM_CREDENTIALS).
    
    For symmetry, forbid MSG_OOB in unix_bpf_recvmsg().
    
    Fixes: 314001f0bf92 ("af_unix: Add OOB support")
    Suggested-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Tested-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
    Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Reviewed-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20240713200218.2140950-2-mhal@xxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5a26e785ce70d..a551be47cb6c6 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2624,10 +2624,49 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
 
 static int unix_stream_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 {
+	struct unix_sock *u = unix_sk(sk);
+	struct sk_buff *skb;
+	int err;
+
 	if (unlikely(READ_ONCE(sk->sk_state) != TCP_ESTABLISHED))
 		return -ENOTCONN;
 
-	return unix_read_skb(sk, recv_actor);
+	mutex_lock(&u->iolock);
+	skb = skb_recv_datagram(sk, MSG_DONTWAIT, &err);
+	mutex_unlock(&u->iolock);
+	if (!skb)
+		return err;
+
+#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
+	if (unlikely(skb == READ_ONCE(u->oob_skb))) {
+		bool drop = false;
+
+		unix_state_lock(sk);
+
+		if (sock_flag(sk, SOCK_DEAD)) {
+			unix_state_unlock(sk);
+			kfree_skb(skb);
+			return -ECONNRESET;
+		}
+
+		spin_lock(&sk->sk_receive_queue.lock);
+		if (likely(skb == u->oob_skb)) {
+			WRITE_ONCE(u->oob_skb, NULL);
+			drop = true;
+		}
+		spin_unlock(&sk->sk_receive_queue.lock);
+
+		unix_state_unlock(sk);
+
+		if (drop) {
+			WARN_ON_ONCE(skb_unref(skb));
+			kfree_skb(skb);
+			return -EAGAIN;
+		}
+	}
+#endif
+
+	return recv_actor(sk, skb);
 }
 
 static int unix_stream_read_generic(struct unix_stream_read_state *state,
diff --git a/net/unix/unix_bpf.c b/net/unix/unix_bpf.c
index bd84785bf8d6c..bca2d86ba97d8 100644
--- a/net/unix/unix_bpf.c
+++ b/net/unix/unix_bpf.c
@@ -54,6 +54,9 @@ static int unix_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
 	struct sk_psock *psock;
 	int copied;
 
+	if (flags & MSG_OOB)
+		return -EOPNOTSUPP;
+
 	if (!len)
 		return 0;