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bpf: Fix sk_psock refcnt leak when receiving message 

tcp_bpf_recvmsg() invokes sk_psock_get(), which returns a reference of
the specified sk_psock object to "psock" with increased refcnt.

When tcp_bpf_recvmsg() returns, local variable "psock" becomes invalid,
so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in several exception handling paths
of tcp_bpf_recvmsg(). When those error scenarios occur such as "flags"
includes MSG_ERRQUEUE, the function forgets to decrease the refcnt
increased by sk_psock_get(), causing a refcnt leak.

Fix this issue by calling sk_psock_put() or pulling up the error queue
read handling when those error scenarios occur.

Fixes: e7a5f1f1cd ("bpf/sockmap: Read psock ingress_msg before sk_receive_queue")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/1587872115-42805-1-git-send-email-xiyuyang19@fudan.edu.cn
This commit is contained in:
Xiyu Yang 2020-04-26 11:35:15 +08:00 committed by Daniel Borkmann
parent 37255e7a8f
commit 18f02ad19e
1 changed files with 6 additions and 3 deletions
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9
net/ipv4/tcp_bpf.c
View File

@ -262,14 +262,17 @@ static int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
struct sk_psock *psock; struct sk_psock *psock;
int copied, ret; int copied, ret;
if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
psock = sk_psock_get(sk); psock = sk_psock_get(sk);
if (unlikely(!psock)) if (unlikely(!psock))
return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len); return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
if (!skb_queue_empty(&sk->sk_receive_queue) && if (!skb_queue_empty(&sk->sk_receive_queue) &&
sk_psock_queue_empty(psock)) sk_psock_queue_empty(psock)) {
sk_psock_put(sk, psock);
return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len); return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
}
lock_sock(sk); lock_sock(sk);
msg_bytes_ready: msg_bytes_ready:
copied = __tcp_bpf_recvmsg(sk, psock, msg, len, flags); copied = __tcp_bpf_recvmsg(sk, psock, msg, len, flags);