6.10-stable review patch. If anyone has any objections, please let me know.
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From: Michal Luczaj mhal@rbox.co
[ 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 BPF redirecting does not account for that: when an OOB packet is moved between sockets, `oob_skb` is left outdated.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@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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 142f56770b77f..11cb5badafb6d 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 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;