Racy interactions between dirty vram tracking and paging log dirty hypercalls Activation of log dirty mode done by XEN_DMOP_track_dirty_vram (was named HVMOP_track_dirty_vram before Xen 4.9) is racy with ongoing log dirty hypercalls. A suitably timed call to XEN_DMOP_track_dirty_vram can enable log dirty while another CPU is still in the process of tearing down the structures related to a previously enabled log dirty mode (XEN_DOMCTL_SHADOW_OP_OFF). This is due to lack of mutually exclusive locking between both operations and can lead to entries being added in already freed slots, resulting in a memory leak.
The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Xen | Xen | 4.0.0 (including) | 4.12.0 (excluding) |
| Xen | Xen | 4.13.0 (including) | 4.14.0 (excluding) |
| Xen | Xen | 4.15.0 (including) | 4.16.0 (excluding) |
| Xen | Ubuntu | bionic | * |
| Xen | Ubuntu | impish | * |
| Xen | Ubuntu | kinetic | * |
| Xen | Ubuntu | lunar | * |
| Xen | Ubuntu | mantic | * |
| Xen | Ubuntu | trusty | * |
| Xen | Ubuntu | xenial | * |
Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.