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Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot
From: |
Amit Shah |
Subject: |
Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot |
Date: |
Fri, 17 Jun 2011 14:14:27 +0530 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On (Fri) 17 Jun 2011 [09:47:31], Markus Armbruster wrote:
> Amit Shah <address@hidden> writes:
>
> > On (Thu) 16 Jun 2011 [13:38:49], Luiz Capitulino wrote:
> >> If I start qemu with:
> >>
> >> # qemu -hda disks/test.img -enable-kvm -m 1G -snapshot \
> >> -device virtio-serial \
> >> -chardev socket,host=localhost,port=1234,server,nowait,id=foo \
> >> -device virtserialport,chardev=foo,name=org.qemu.guest_agent
> >>
> >> I get a segfault when booting a Fedora 14 guest. The backtrace says:
> >>
> >> Program terminated with signal 11, Segmentation fault.
> >> #0 0x0000000000420850 in handle_control_message (vser=0x3732bd0,
> >> buf=0x2c173e0, len=8) at
> >> /home/lcapitulino/src/qmp-unstable/hw/virtio-serial-bus.c:335
> >> 335 info = DO_UPCAST(VirtIOSerialPortInfo, qdev, port->dev.info);
> >
> > Strange, I've not seen it so far in my testing (neither in the daily
> > test runs of the virtio-serial testsuite).
> >
> >> I've also bisected this and git points out to commit:
> >>
> >> commit a15bb0d6a981de749452a5180fc8084d625671da
> >> Author: Markus Armbruster <address@hidden>
> >> Date: Wed May 25 14:21:13 2011 +0200
> >>
> >> virtio-serial: Drop redundant VirtIOSerialPort member info
> >>
> >> I think what's happening is that the device is not initialized on a
> >> VIRTIO_CONSOLE_DEVICE_READY event.
>
> Really?
>
> I believe the device is initialized just fine, but the message refers to
> a nonexistant port. The check after find_port_by_id() suggests that's
> expected for VIRTIO_CONSOLE_DEVICE_READY.
What's happening is VIRTIO_CONSOLE_DEVICE_READY is a message for the
whole device, not for an individual port. So port is NULL. All other
messages (currently) are port-specific, so they have 'port' set to
something. The commit message needs to be tweaked for this.
>
> >> Moving the DO_UPCAST() call to
> >> the other events fixes the problem to me.
> >>
> >> Signed-off-by: Luiz Capitulino <address@hidden>
> >> ---
> >> hw/virtio-serial-bus.c | 4 ++--
> >> 1 files changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
> >> index 9a12104..579f676 100644
> >> --- a/hw/virtio-serial-bus.c
> >> +++ b/hw/virtio-serial-bus.c
> >> @@ -332,8 +332,6 @@ static void handle_control_message(VirtIOSerial *vser,
> >> void *buf, size_t len)
> >> if (!port && cpkt.event != VIRTIO_CONSOLE_DEVICE_READY)
> >> return;
> >>
> >> - info = DO_UPCAST(VirtIOSerialPortInfo, qdev, port->dev.info);
> >> -
> >
> > Ah - this missed the !port check. It should be possible to do this in
> > a 'if (port)' block instead of replicating in the individual case
> > statements.
>
> You might have to do something like info = port ? DO_UPCAST(...) : NULL
> to avoid warnings about info used uninitialized.
That won't happen -- in the case where port is NULL, we shouldn't try
to use info. If we do get such a warning, it means there's a bug :-)
Amit
- [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Luiz Capitulino, 2011/06/16
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Amit Shah, 2011/06/17
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Markus Armbruster, 2011/06/17
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot,
Amit Shah <=
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Luiz Capitulino, 2011/06/17
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Luiz Capitulino, 2011/06/17
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Amit Shah, 2011/06/17
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Luiz Capitulino, 2011/06/17
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Amit Shah, 2011/06/17
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Blue Swirl, 2011/06/18
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Amit Shah, 2011/06/22
- Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot, Blue Swirl, 2011/06/26
- Re: [Qemu-devel] 80-column rule and breaking output statements, Amit Shah, 2011/06/27