From: Xiyu Yang xiyuyang19@fudan.edu.cn
commit 18f02ad19e2c2a1d9e1d55a4e1c0cbf51419151c upstream.
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: e7a5f1f1cd000 ("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@fud... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/ipv4/tcp_bpf.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -121,14 +121,17 @@ int tcp_bpf_recvmsg(struct sock *sk, str struct sk_psock *psock; int copied, ret;
+ if (unlikely(flags & MSG_ERRQUEUE)) + return inet_recv_error(sk, msg, len, addr_len); + psock = sk_psock_get(sk); if (unlikely(!psock)) 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) && - 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); + } lock_sock(sk); msg_bytes_ready: copied = __tcp_bpf_recvmsg(sk, psock, msg, len, flags);