|Summary:||CVE-2014-0049 kernel: kvm: mmio_fragments out-of-the-bounds access|
|Product:||[Other] Security Response||Reporter:||Petr Matousek <pmatouse>|
|Component:||vulnerability||Assignee:||Red Hat Product Security <security-response-team>|
|Status:||CLOSED NOTABUG||QA Contact:|
|Version:||unspecified||CC:||agordeev, anton, aquini, dhoward, drjones, fhrbata, kernel-mgr, lwang, npajkovs, pbonzini, pholasek, security-response-team|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2014-02-06 18:13:55 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Bug Depends On:||1071836, 1071837|
Description Petr Matousek 2014-02-06 18:09:54 UTC
The problem occurs when the guest performs a pusha with the stack address pointing to an mmio address (or an invalid guest physical address) to start with, but then extending into an ordinary guest physical address. When doing repeated emulated pushes emulator_read_write sets mmio_needed to 1 on the first one. On a later push when the stack points to regular memory, mmio_nr_fragments is set to 0, but mmio_is_needed is not set to 0. As a result, KVM exits to userspace, and then returns to complete_emulated_mmio. In complete_emulated_mmio vcpu->mmio_cur_fragment is incremented. The termination condition of vcpu->mmio_cur_fragment == vcpu->mmio_nr_fragments is never achieved. The code bounces back and fourth to userspace incrementing mmio_cur_fragment past it's buffer. If the guest does nothing else it eventually leads to a a crash on a memcpy from invalid memory address. However if a guest code can cause the vm to be destoryed in another vcpu with excellent timing, then kvm_clear_async_pf_completion_queue can be used by the guest to control the data that's pointed to by the call to cancel_work_item, which can be used to gain execution. Introduced by: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f78146b0f Acknowledgements: Red Hat would like to thank Lars Bull of Google for reporting this issue.
Comment 1 Petr Matousek 2014-02-06 18:13:55 UTC
Statement: Not vulnerable. This issue did not affect the versions of kvm package as shipped with Red Hat Enterprise Linux 5 as they did not backport the upstream kvm commit that introduced this issue. This issue did not affect the versions of Linux kernel as shipped Red Hat Enterprise Linux 6 as they did not backport the upstream kvm commit that introduced this issue. This issue did not affect the versions of Linux kernel as shipped Red Hat Enterprise MRG as they did not provide support for the KVM subsystem.
Comment 2 Petr Matousek 2014-03-03 09:28:36 UTC
Comment 4 Petr Matousek 2014-03-03 09:34:07 UTC
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 1071837]
Comment 5 Fedora Update System 2014-03-06 08:09:42 UTC
kernel-3.13.5-202.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.
Comment 6 Fedora Update System 2014-03-09 04:38:20 UTC
kernel-3.13.5-103.fc19 has been pushed to the Fedora 19 stable repository. If problems still persist, please make note of it in this bug report.