Re: [Qemu-devel] [PATCH 2/2] io: fix qio_channel_socket_accept err handling

[Peter Xu]

On Wed, Aug 02, 2017 at 10:30:20AM +0100, Daniel P. Berrange wrote:
> On Wed, Aug 02, 2017 at 11:25:21AM +0800, Peter Xu 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.
> > 
> > At the same time, move the trace_qio_channel_socket_accept_fail() after
> > the if check on EINTR. Two reasons:
> > 
> > 1. when EINTR happened, it's not really a fault (we should just try
> >again), so we should not log with an "accept failure".
> > 
> > 2. trace_*() functions may overwrite errno, then the old errno will be
> >missing. We need to either check errno before trace_*() calls, or
> >reserve the errno.
> > 
> > Signed-off-by: Peter Xu 
> > ---
> >  io/channel-socket.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/io/channel-socket.c b/io/channel-socket.c
> > index 53386b7..442f230 100644
> > --- a/io/channel-socket.c
> > +++ b/io/channel-socket.c
> > @@ -340,10 +340,11 @@ qio_channel_socket_accept(QIOChannelSocket *ioc,
> >  cioc->fd = qemu_accept(ioc->fd, (struct sockaddr *)>remoteAddr,
> > >remoteAddrLen);
> >  if (cioc->fd < 0) {
> > -trace_qio_channel_socket_accept_fail(ioc);
> >  if (errno == EINTR) {
> >  goto retry;
> >  }
> > +trace_qio_channel_socket_accept_fail(ioc);
> > +error_setg_errno(errp, errno, "Unable to accept connection");
> 
> Err, you're still clobbering errno in trace_qio_channel_socket_accept_fail
> before calling error_setg_errno

Oops! I'll do a quick respin.  Thanks for pointing out.

-- 
Peter Xu

Re: [Qemu-devel] [PATCH 2/2] io: fix qio_channel_socket_accept err handling

[Juan Quintela]

Peter Xu  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.
>
> At the same time, move the trace_qio_channel_socket_accept_fail() after
> the if check on EINTR. Two reasons:
>
> 1. when EINTR happened, it's not really a fault (we should just try
>again), so we should not log with an "accept failure".
>
> 2. trace_*() functions may overwrite errno, then the old errno will be
>missing. We need to either check errno before trace_*() calls, or
>reserve the errno.
>
> Signed-off-by: Peter Xu 

Reviewed-by: Juan Quintela 

[Qemu-devel] [PATCH 2/2] io: fix qio_channel_socket_accept err handling

[Peter Xu]

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.

At the same time, move the trace_qio_channel_socket_accept_fail() after
the if check on EINTR. Two reasons:

1. when EINTR happened, it's not really a fault (we should just try
   again), so we should not log with an "accept failure".

2. trace_*() functions may overwrite errno, then the old errno will be
   missing. We need to either check errno before trace_*() calls, or
   reserve the errno.

Signed-off-by: Peter Xu 
---
 io/channel-socket.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/io/channel-socket.c b/io/channel-socket.c
index 53386b7..442f230 100644
--- a/io/channel-socket.c
+++ b/io/channel-socket.c
@@ -340,10 +340,11 @@ qio_channel_socket_accept(QIOChannelSocket *ioc,
 cioc->fd = qemu_accept(ioc->fd, (struct sockaddr *)>remoteAddr,
>remoteAddrLen);
 if (cioc->fd < 0) {
-trace_qio_channel_socket_accept_fail(ioc);
 if (errno == EINTR) {
 goto retry;
 }
+trace_qio_channel_socket_accept_fail(ioc);
+error_setg_errno(errp, errno, "Unable to accept connection");
 goto error;
 }
 
-- 
2.7.4