CVE-2020-25221

Name	CVE-2020-25221
Description	get_gate_page in mm/gup.c in the Linux kernel 5.7.x and 5.8.x before 5.8.7 allows privilege escalation because of incorrect reference counting (caused by gate page mishandling) of the struct page that backs the vsyscall page. The result is a refcount underflow. This can be triggered by any 64-bit process that can use ptrace() or process_vm_readv(), aka CID-9fa2dd946743.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
linux (PTS)	buster	4.19.249-2	fixed
	buster (security)	4.19.269-1	fixed
	bullseye	5.10.158-2	fixed
	bullseye (security)	5.10.162-1	fixed
	bookworm, sid	6.1.20-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version
linux	source	stretch	(not affected)
linux	source	buster	(not affected)
linux	source	(unstable)	5.8.7-1

Notes

[buster] - linux <not-affected> (Vulnerable code introduced later)
[stretch] - linux <not-affected> (Vulnerable code introduced later)
https://git.kernel.org/linus/9fa2dd946743ae6f30dc4830da19147bf100a7f2