CVE-2019-15794

Name	CVE-2019-15794
Description	Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, both replace vma->vm_file in their mmap handlers. On error the original value is not restored, and the reference is put for the file to which vm_file points. On upstream kernels this is not an issue, as no callers dereference vm_file following after call_mmap() returns an error. However, the aufs patchs change mmap_region() to replace the fput() using a local variable with vma_fput(), which will fput() vm_file, leading to a refcount underflow.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
linux (PTS)	jessie, jessie (lts)	3.16.84-1	fixed
	stretch (security)	4.9.320-2	fixed
	stretch (lts), stretch	4.9.320-3	fixed
	buster	4.19.249-2	vulnerable
	buster (security)	4.19.269-1	vulnerable
	bullseye	5.10.158-2	vulnerable
	bullseye (security)	5.10.162-1	vulnerable
	bookworm	6.1.15-1	fixed
	sid	6.1.20-1	fixed

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

Package	Type	Release	Fixed Version	Urgency
linux	source	wheezy	(unfixed)	end-of-life
linux	source	jessie	(not affected)
linux	source	stretch	(not affected)
linux	source	(unstable)	5.16.7-1

Notes

[stretch] - linux <not-affected> (overlayfs passes through mmap)
[jessie] - linux <not-affected> (overlayfs not present)
https://bugs.launchpad.net/bugs/1850994