CVE-2019-15794

NameCVE-2019-15794
DescriptionOverlayfs 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.
SourceCVE (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 PackageReleaseVersionStatus
linux (PTS)buster4.19.249-2vulnerable
buster (security)4.19.260-1vulnerable
bullseye5.10.140-1vulnerable
bullseye (security)5.10.149-2vulnerable
bookworm6.0.10-1fixed
sid6.0.10-2fixed

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
linuxsourcejessie(not affected)
linuxsourcestretch(not affected)
linuxsource(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

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