A bug in QEMU could cause a guest I/O operation otherwise addressed to an arbitrary disk offset to be targeted to offset 0 instead (potentially overwriting the VMs boot code). This could be used, for example, by L2 guests with a virtual disk (vdiskL2) stored on a virtual disk of an L1 (vdiskL1) hypervisor to read and/or write data to LBA 0 of vdiskL1, potentially gaining control of L1 at its next reboot.
The product utilizes multiple threads or processes to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Qemu | Qemu | * | 8.2.0 (excluding) |
| Red Hat Enterprise Linux 8 | RedHat | virt-devel:rhel-8100020240314161907.e155f54d | * |
| Red Hat Enterprise Linux 8 | RedHat | virt:rhel-8100020240314161907.e155f54d | * |
| Red Hat Enterprise Linux 9 | RedHat | qemu-kvm-17:8.2.0-11.el9_4 | * |
| Qemu | Ubuntu | bionic | * |
| Qemu | Ubuntu | devel | * |
| Qemu | Ubuntu | focal | * |
| Qemu | Ubuntu | jammy | * |
| Qemu | Ubuntu | lunar | * |
| Qemu | Ubuntu | mantic | * |
| Qemu | Ubuntu | noble | * |
| Qemu | Ubuntu | oracular | * |
| Qemu | Ubuntu | trusty | * |
| Qemu | Ubuntu | trusty/esm | * |
| Qemu | Ubuntu | xenial | * |
Synchronization refers to a variety of behaviors and mechanisms that allow two or more independently-operating processes or threads to ensure that they operate on shared resources in predictable ways that do not interfere with each other. Some shared resource operations cannot be executed atomically; that is, multiple steps must be guaranteed to execute sequentially, without any interference by other processes. Synchronization mechanisms vary widely, but they may include locking, mutexes, and semaphores. When a multi-step operation on a shared resource cannot be guaranteed to execute independent of interference, then the resulting behavior can be unpredictable. Improper synchronization could lead to data or memory corruption, denial of service, etc.