From: Eric Dumazet <eric.duma...@gmail.com>
Date: Wed, 02 Nov 2016 14:41:50 -0700
> From: Eric Dumazet <eduma...@google.com>
>
> After my commit, tcp_sendmsg() might restart its loop after
> processing socket backlog.
>
> If sk_err is set, we blindly return an error, even though we
> copied data to user space before.
>
> We should instead return number of bytes that could be copied,
> otherwise user space might resend data and corrupt the stream.
>
> This might happen if another thread is using recvmsg(MSG_ERRQUEUE)
> to process timestamps.
>
> Issue was diagnosed by Soheil and Willem, big kudos to them !
>
> Fixes: d41a69f1d390f ("tcp: make tcp_sendmsg() aware of socket backlog")
> Signed-off-by: Eric Dumazet <eduma...@google.com>
Applied and queued up for -stable.
