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bpf, sockmap: fix bpf_tcp_sendmsg sock error handling

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While working on bpf_tcp_sendmsg() code, I noticed that when a
sk->sk_err is set we error out with err = sk->sk_err. However
this is problematic since sk->sk_err is a positive error value
and therefore we will neither go into sk_stream_error() nor will
we report an error back to user space. I had this case with EPIPE
and user space was thinking sendmsg() succeeded since EPIPE is
a positive value, thinking we submitted 32 bytes. Fix it by
negating the sk->sk_err value.

Fixes: 4f738adba3 ("bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2018-08-08 19:23:13 +02:00 committed by Alexei Starovoitov
parent 74682128c6
commit 5121700b34
1 changed files with 1 additions and 1 deletions
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2
kernel/bpf/sockmap.c
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@ -1053,7 +1053,7 @@ static int bpf_tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
int copy;
if (sk->sk_err) {
err = sk->sk_err;
err = -sk->sk_err;
goto out_err;
}