Use RCU lock to protect sk_socket, preventing concurrent close and release
by another thread.
Because TCP/UDP are already within a relatively large critical section:
'''
ip_local_deliver_finish
rcu_read_lock
ip_protocol_deliver_rcu
tcp_rcv/udp_rcv
rcu_read_unlock
'''
Adding rcu_read_{un}lock() at the entrance and exit of sk_data_ready
will not increase performance overhead.
Fixes: c63829182c37 ("af_unix: Implement ->psock_update_sk_prot()")
Reported-by: syzbot+dd90a702f518e0eac...@syzkaller.appspotmail.com
Closes:
https://lore.kernel.org/bpf/6734c033.050a0220.2a2fcc.0015....@google.com/
Reviewed-by: Cong Wang <xiyou.wangc...@gmail.com>
Reviewed-by: John Fastabend <john.fastab...@gmail.com>
Signed-off-by: Jiayuan Chen <jiayuan.c...@linux.dev>
---
net/core/skmsg.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 0ddc4c718833..1b71ae1d1bf5 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -1222,27 +1222,35 @@ static int sk_psock_verdict_recv(struct sock *sk,
struct sk_buff *skb)
static void sk_psock_verdict_data_ready(struct sock *sk)
{
- struct socket *sock = sk->sk_socket;
+ struct socket *sock;
const struct proto_ops *ops;
int copied;
trace_sk_data_ready(sk);
+ /* We need RCU to prevent the sk_socket from being released.
+ * Especially for Unix sockets, we are currently in the process
+ * context and do not have RCU protection.
+ */
+ rcu_read_lock();
+ sock = sk->sk_socket;
if (unlikely(!sock))
- return;
+ goto unlock;
+
ops = READ_ONCE(sock->ops);
if (!ops || !ops->read_skb)
- return;
+ goto unlock;
+
copied = ops->read_skb(sk, sk_psock_verdict_recv);
if (copied >= 0) {
struct sk_psock *psock;
- rcu_read_lock();
psock = sk_psock(sk);
if (psock)
sk_psock_data_ready(sk, psock);
- rcu_read_unlock();
}
+unlock:
+ rcu_read_unlock();
}
void sk_psock_start_verdict(struct sock *sk, struct sk_psock *psock)
--
2.47.1
