** Patch added: "Proposed fix for trusty" https://bugs.launchpad.net/qemu/+bug/1581936/+attachment/4864874/+files/qemu-trusty.debdiff
-- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1581936 Title: Frozen Windows 7 VMs with VGA CVE-2016-3712 fix (2.6.0 and 2.5.1.1) Status in QEMU: Fix Released Bug description: 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 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1581936/+subscriptions
