CVE-2021-47566

Name of the Vulnerable Software and Affected Versions: Linux kernel versions prior to 5.15.0

Description: The vulnerability is related to the proc/vmcore component of the Linux kernel. It is caused by a buffer overflow when clearing a user buffer, which can lead to a permissions violation. The issue can be triggered by copying the vmcore via "cp" with a virtio-mem device that registers a vmcore cb and has some logically unplugged memory inside an added Linux memory block. Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access Prevention (SMAP)" that can detect wrong access from the kernel to user buffers, triggering a permissions violation on wrong access. The vulnerability can cause a BUG and a page fault, leading to a crash.

Recommendations: To resolve the issue, properly use the clear user() function when dealing with a user buffer, instead of memset. This can be achieved by updating the Linux kernel to a version that includes the fix for the proc/vmcore vulnerability. At the moment, there is no information about a newer version that contains a fix for this vulnerability.