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af_unix: Disable MSG_OOB handling for sockets in sockmap/sockhash

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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an OOB packet is moved between sockets, `oob_skb` is left outdated.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: 314001f0bf ("af_unix: Add OOB support")
Suggested-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Jakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20240713200218.2140950-2-mhal@rbox.co
This commit is contained in:
Michal Luczaj 2024-07-13 21:41:38 +02:00 committed by Daniel Borkmann
parent 3c870059e9
commit 638f326043
2 changed files with 43 additions and 1 deletions
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41
net/unix/af_unix.c
View File

@ -2721,10 +2721,49 @@ 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,

3
net/unix/unix_bpf.c
View File

@ -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;