CVE-2019-15794
Reference counting error in overlayfs/shiftfs error path when used in conjuction with aufs
- Published
- Apr 23, 2020
- Updated
- Sep 16, 2024
- Assigning CNA
- canonical
- Evidence observed
- Nov 20, 2019
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:HLow · next 30 days
- Percentile
- 66.6%
- Model date
- Oct 19, 2026
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Summary
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.
Sources
- Ubuntu 19.10 - ubuntu-aufs-modified mmap_region() Breaks Refcounting in overlayfs/shiftfs Error PathExploit
Google Security Research · linux · Nov 20, 2019
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