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an OOB packet is moved between sockets, `oob_skb` is left outdated.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().
Suggested-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Fixes: 314001f0bf92 ("af_unix: Add OOB support")
Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Reviewed-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
---
net/unix/af_unix.c | 41 ++++++++++++++++++++++++++++++++++++++++-
net/unix/unix_bpf.c | 3 +++
2 files changed, 43 insertions(+), 1 deletion(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 142f56770b77..11cb5badafb6 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2667,10 +2667,49 @@ 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 bd84785bf8d6..bca2d86ba97d 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;
--
2.45.2
