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Diffstat (limited to 'results/classifier/accel-gemma3:12b/kvm/1581936')
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1 files changed, 67 insertions, 0 deletions
diff --git a/results/classifier/accel-gemma3:12b/kvm/1581936 b/results/classifier/accel-gemma3:12b/kvm/1581936 new file mode 100644 index 000000000..aa46017a6 --- /dev/null +++ b/results/classifier/accel-gemma3:12b/kvm/1581936 @@ -0,0 +1,67 @@ + +Frozen Windows 7 VMs with VGA CVE-2016-3712 fix (2.6.0 and 2.5.1.1) + +Hi, + +As already posted on the QEMU devel list [1] I stumbled upon a problem with QEMU in version 2.5.1.1 and 2.6.0. + +the VM shows Windows loading +files for the installation, then the "Starting Windows" screen appears +here it hangs and never continues. + +Changing the "-vga" option to cirrus solves this, the installation can +proceed and finish. When changing back to std (or also qxl, vmware) the +installed VM also hangs on the "Starting Windows" screen while qemu +showing a little but no excessive load. + +This phenomena appears also with QEMU 2.6.0 but not with 2.6.0-rc4, a +git bisect shows fd3c136b3e1482cd0ec7285d6bc2a3e6a62c38d7 (vga: make +sure vga register setup for vbe stays intact (CVE-2016-3712)) as the +culprit for this regression, as its a fix for a DoS its not an option to +just revert it, I guess. + +The bisect log is: + +git bisect start +# bad: [bfc766d38e1fae5767d43845c15c79ac8fa6d6af] Update version for v2.6.0 release +git bisect bad bfc766d38e1fae5767d43845c15c79ac8fa6d6af +# good: [975eb6a547f809608ccb08c221552f666611af25] Update version for v2.6.0-rc4 release +git bisect good 975eb6a547f809608ccb08c221552f666611af25 +# good: [2068192dcccd8a80dddfcc8df6164cf9c26e0fc4] vga: update vga register setup on vbe changes +git bisect good 2068192dcccd8a80dddfcc8df6164cf9c26e0fc4 +# bad: [53db932604dfa7bb9241d132e0173894cf54261c] Merge remote-tracking branch 'remotes/kraxel/tags/pull-vga-20160509-1' into staging +git bisect bad 53db932604dfa7bb9241d132e0173894cf54261c +# bad: [fd3c136b3e1482cd0ec7285d6bc2a3e6a62c38d7] vga: make sure vga register setup for vbe stays intact (CVE-2016-3712). +git bisect bad fd3c136b3e1482cd0ec7285d6bc2a3e6a62c38d7 +# first bad commit: [fd3c136b3e1482cd0ec7285d6bc2a3e6a62c38d7] vga: make sure vga register setup for vbe stays intact (CVE-2016-3712). + + +I could reproduce that with QEMU 2.5.1 and QEMU 2.6 on a Debian derivate +(Promox VE) with 4.4 Kernel and also with QEMU 2.6 on an Arch Linux +System with a 4.5 Kernel, so it should not be host distro depended. Both +machines have Intel x86_64 processors. +The problem should be reproducible with said Versions or a build from +git including the above mentioned commit (fd3c136) by starting a VM with +an Windows 7 ISO, e.g.: + +Freezing installation (as vga defaults to std I marked it as optional): +./x86_64-softmmu/qemu-system-x86_64 -boot d -cdrom win7.iso -m 1024 [-vga (std|qxl|vmware)] + +Working installation: +./x86_64-softmmu/qemu-system-x86_64 -boot d -cdrom win7.iso -m 1024 -vga cirrus + +If someone has already an installed Windows 7 VM this behaviour should be +also observable when trying to start it with the new versions of QEMU. + +Noteworthy may be that Windows 10 is working, I do not had time to get +other Windows versions and test them, I'll do that as soon as possible. +Various Linux system also seems do work fine, at least I did not ran +into an issue there yet. + +I also tried testing with SeaBIOS and OVMF as firmware, as initially I +had no idea what broke, both lead to the same result - without the +CVE-2016-3712 fix they both work, with not. +Further, KVM enabled and disabled does not make any difference. + + +[1] http://lists.nongnu.org/archive/html/qemu-devel/2016-05/msg02416.html \ No newline at end of file |