Re: [Qemu-devel] [RFC 03/29] io: fix qio_channel_socket_accept err handling

[Daniel P. Berrange]

On Tue, Aug 01, 2017 at 10:25:19AM +0800, Peter Xu wrote:
> On Mon, Jul 31, 2017 at 05:53:39PM +0100, Dr. David Alan Gilbert wrote:
> > * Peter Xu (address@hidden) wrote:
> > > When accept failed, we should setup errp with the reason. More
> > > importantly, the caller may assume errp be non-NULL when error happens,
> > > and not setting the errp may crash QEMU.
> > > 
> > > Signed-off-by: Peter Xu <address@hidden>
> > > ---
> > >  io/channel-socket.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/io/channel-socket.c b/io/channel-socket.c
> > > index 53386b7..7bc308e 100644
> > > --- a/io/channel-socket.c
> > > +++ b/io/channel-socket.c
> > > @@ -344,6 +344,7 @@ qio_channel_socket_accept(QIOChannelSocket *ioc,
> > >          if (errno == EINTR) {
> > >              goto retry;
> > >          }
> > > +        error_setg_errno(errp, errno, "Unable to accept connection");
> > >          goto error;
> > 
> > OK, but this code actually has a bigger problem as well:
> > 
> > the original is:
> > 
> >     cioc->fd = qemu_accept(ioc->fd, (struct sockaddr *)&cioc->remoteAddr,
> >                            &cioc->remoteAddrLen);
> >     if (cioc->fd < 0) {
> >         trace_qio_channel_socket_accept_fail(ioc);
> >         if (errno == EINTR) {
> >             goto retry;
> >         }
> >         goto error;
> >     }
> > 
> > Stefan confirmed that trace_ doesn't preserve errno; so the if
> > following it is wrong.  It needs to preserve errno.
> 
> Ah... If so, not sure whether we can do the reservation in trace codes
> in general?
> 
> For this one, I can just move the trace_*() below the errno check.
> After all, if EINTR is got, it's not really a fail, so imho we should
> not trace it with "accept fail".

Agreed, we just need to move the trace below the if.


Regards,
Daniel
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