From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:45288) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QXUfV-0008Nt-2V for qemu-devel@nongnu.org; Fri, 17 Jun 2011 04:44:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QXUfT-0004x2-Km for qemu-devel@nongnu.org; Fri, 17 Jun 2011 04:44:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5386) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QXUfS-0004wn-Op for qemu-devel@nongnu.org; Fri, 17 Jun 2011 04:44:43 -0400 Date: Fri, 17 Jun 2011 14:14:27 +0530 From: Amit Shah Message-ID: <20110617084427.GC18513@amit-x200.redhat.com> References: <20110616133849.02fb4bea@doriath> <20110617064736.GA18513@amit-x200.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH] virtio-serial: Fix segfault on guest boot List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: mdroth@linux.vnet.ibm.com, qemu-devel , Luiz Capitulino On (Fri) 17 Jun 2011 [09:47:31], Markus Armbruster wrote: > Amit Shah 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 > >> 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 > >> --- > >> 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