Linux · Linux Kernel · CVE-2020-29569
**Name of the Vulnerable Software and Affected Versions**
Linux kernel versions through 5.10.1
Xen versions through 4.14.x
**Description**
An issue in the Linux kernel PV block backend may cause a pointer to be re-used after it was freed. This occurs when the kernel thread handler does not have time to reset `ring->xenblkd` to NULL if the frontend quickly toggles between connect and disconnect states. A misbehaving guest can trigger a dom0 crash by continuously connecting/disconnecting a block frontend, potentially leading to privilege escalation and information leaks. This issue affects systems with a Linux blkback.
**Recommendations**
For Linux kernel versions through 5.10.1, update to a version that includes the fix for this issue.
For Xen versions through 4.14.x, ensure that the Linux kernel used is updated to a version that includes the fix for this issue.
As a temporary workaround, consider restricting access to the block backend to minimize the risk of exploitation.