Re: [Qemu-devel] [PATCH] socket: don't attempt to reconnect a TCP socket in server mode

[Richard W.M. Jones]

On Wed, Sep 05, 2012 at 02:01:36PM -0500, Anthony Liguori wrote:
> Commit c3767ed0eb5d0bb25fe409ae5dec06e3411ff1b6 introduced a possible SEGV 
> when
> using a socket chardev with server=on because it assumes that all TCP sockets
> are in client mode.
> 
> This patch adds a check to only reconnect when in client mode.
> 
> Cc: Lei Li <address@hidden>
> Reported-by: Michael Roth <address@hidden>
> Signed-off-by: Anthony Liguori <address@hidden>
> ---
>  qemu-char.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/qemu-char.c b/qemu-char.c
> index 398baf1..767da93 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -2148,10 +2148,12 @@ static int tcp_chr_write(CharDriverState *chr, const 
> uint8_t *buf, int len)
>      TCPCharDriver *s = chr->opaque;
>      if (s->connected) {
>          return send_all(s->fd, buf, len);
> -    } else {
> +    } else if (s->listen_fd == -1) {
>          /* (Re-)connect for unconnected writing */
>          tcp_chr_connect(chr);
>          return 0;
> +    } else {
> +        return len;
>      }
>  }

Hi Anthony,

I just came around this patch when I was trying to fix this
bug: https://bugzilla.redhat.com/show_bug.cgi?id=853408
qemu segfaults when trying to write to a serial socket which
is *not* a server socket and has been closed by the other end.

Unfortunately your patch above does not fix it.  Only a
complete revert of c3767ed0eb5d0 fixes it.

I don't understand the purpose of c3767ed0eb5d0 at all.  It
seems to set the s->connected flag and carries on regardless,
happily calling write (-1, ...), which is completely broken.

The other end closed the socket.  There's no one listening on the
other end, and setting the s->connected flag will not help that.

Rich.

-- 
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