CVE-2020-25221

A flaw was found in the get_gate_page in mm/gup.c in the Linux kernel, where it allows privilege escalation due to incorrect reference counting (caused by gate page mishandling) of the struct page that backs the vsyscall page. The result is a refcount underflow. This flaw is triggered by any 64-bit process that can use ptrace() or process_vm_readv(). The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.

Mitigation

The issue relevant starting from kernel v5.6 and possible to prevent the issue from triggering by booting with vsyscall=xonly or vsyscall=none.