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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
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Exploits
Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.
Exploit-DB
Ubuntu 19.10 - ubuntu-aufs-modified mmap_region() Breaks Refcounting in overlayfs/shiftfs Error Path
OS impact
Debian Mixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 5.16.7-1 |
| sid | Fixed | 5.16.7-1 |
| forky | Fixed | 5.16.7-1 |
| bullseye | Affected | — |
| bookworm | Fixed | 5.16.7-1 |
Red Hat Fixed 1 release
| Version | Status | Fixed in |
|---|---|---|
| 8 | Fixed | — |
References
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.