| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 5.7 111/388] bpf: tcp: Recv() should return 0 when the peer socket is closed | Date | Wed, 17 Jun 2020 21:03:28 -0400 |
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From: Sabrina Dubroca <sd@queasysnail.net>
[ Upstream commit 2c7269b231194aae23fb90ab65842573a91acbc9 ]
If the peer is closed, we will never get more data, so tcp_bpf_wait_data will get stuck forever. In case we passed MSG_DONTWAIT to recv(), we get EAGAIN but we should actually get 0.
>From man 2 recv:
RETURN VALUE
When a stream socket peer has performed an orderly shutdown, the return value will be 0 (the traditional "end-of-file" return).
This patch makes tcp_bpf_wait_data always return 1 when the peer socket has been shutdown. Either we have data available, and it would have returned 1 anyway, or there isn't, in which case we'll call tcp_recvmsg which does the right thing in this situation.
Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface") Signed-off-by: Sabrina Dubroca <sd@queasysnail.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Jakub Sitnicki <jakub@cloudflare.com> Link: https://lore.kernel.org/bpf/26038a28c21fea5d04d4bd4744c5686d3f2e5504.1591784177.git.sd@queasysnail.net Signed-off-by: Sasha Levin <sashal@kernel.org> --- net/ipv4/tcp_bpf.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index 629aaa9a1eb9..9c5540887fbe 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -242,6 +242,9 @@ static int tcp_bpf_wait_data(struct sock *sk, struct sk_psock *psock, DEFINE_WAIT_FUNC(wait, woken_wake_function); int ret = 0; + if (sk->sk_shutdown & RCV_SHUTDOWN) + return 1; + if (!timeo) return ret; -- 2.25.1
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