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Subject[PATCH 4.18 013/168] bpf, sockmap: fix psock refcount leak in bpf_tcp_recvmsg
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <daniel@iogearbox.net>

[ Upstream commit 15c480efab01197c965ce0562a43ffedd852b8f9 ]

In bpf_tcp_recvmsg() we first took a reference on the psock, however
once we find that there are skbs in the normal socket's receive queue
we return with processing them through tcp_recvmsg(). Problem is that
we leak the taken reference on the psock in that path. Given we don't
really do anything with the psock at this point, move the skb_queue_empty()
test before we fetch the psock to fix this case.

Fixes: 8934ce2fd081 ("bpf: sockmap redirect ingress support")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/sockmap.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -915,6 +915,8 @@ static int bpf_tcp_recvmsg(struct sock *

if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
+ if (!skb_queue_empty(&sk->sk_receive_queue))
+ return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);

rcu_read_lock();
psock = smap_psock_sk(sk);
@@ -925,9 +927,6 @@ static int bpf_tcp_recvmsg(struct sock *
goto out;
rcu_read_unlock();

- if (!skb_queue_empty(&sk->sk_receive_queue))
- return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
-
lock_sock(sk);
bytes_ready:
while (copied != len) {

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