CVE-2019-15794

medium

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.

References

https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=270d16ae48a4dbf1c7e25e94cc3e38b4bea37635

https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=ef81780548d20a786cc77ed4203fca146fd81ce3

https://usn.ubuntu.com/usn/usn-4208-1

https://usn.ubuntu.com/usn/usn-4209-1

Details

Source: MITRE

Published: 2020-04-24

Updated: 2020-05-26

Type: CWE-672

Risk Information

CVSS v2

Base Score: 7.2

Vector: AV:L/AC:L/Au:N/C:C/I:C/A:C

Impact Score: 10

Exploitability Score: 3.9

Severity: HIGH

CVSS v3

Base Score: 6.7

Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Impact Score: 5.9

Exploitability Score: 0.8

Severity: MEDIUM