CVE-2022-48991: linux kernel Use-After-Free — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Any codepath that zaps page table entries must invoke MMU notifiers to ensure that secondary MMUs (like KVM) don't keep accessing pages which aren't mapped anymore. Secondary MMUs don't hold their own references to pages that are mirrored over, so failing to notify them can lead to page use-after-free. I'm marking this as addressing an issue introduced in commit f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of the security impact of this only came in commit 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP"), which actually omitted flushes for the removal of present PTEs, not just for the removal of empty page tables.

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CVSS v3.1 Score

7.8

HIGH

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

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.8 — 4.9.337
linux	linux_kernel	4.10 — 4.14.303
linux	linux_kernel	4.15 — 4.19.270
linux	linux_kernel	4.20 — 5.4.227
linux	linux_kernel	5.5 — 5.10.159
linux	linux_kernel	5.11 — 5.15.83
linux	linux_kernel	5.16 — 6.0.13
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/1a3f8c6cd29d9078cc81b29d39d0e9ae1d6a03c3 https://git.kernel.org/stable/c/275c626c131cfe141beeb6c575e31fa53d32da19 https://git.kernel.org/stable/c/5450535901d89a5dcca5fbbc59a24fe89caeb465 https://git.kernel.org/stable/c/5ffc2a75534d9d74d49760f983f8eb675fa63d69 https://git.kernel.org/stable/c/7f445ca2e0e59c7971d0b7b853465e50844ab596 https://git.kernel.org/stable/c/c23105673228c349739e958fa33955ed8faddcaf https://git.kernel.org/stable/c/f268f6cf875f3220afc77bdd0bf1bb136eb54db9 https://git.kernel.org/stable/c/ff2a1a6f869650aec99e9d070b5ab625bfbc5bc3

Frequently Asked Questions

What is CVE-2022-48991? +

In the Linux kernel, the following vulnerability has been resolved: mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Any codepath that zaps page table entries must invoke MMU notifiers to ensure that secondary MMUs (like KVM) don't keep accessing pages which aren't mapped anymore. Secondary MMUs don't hold their own references to pages that are mirrored over, so failing to notify them can lead to page use-after-free. I'm marking this as addressing an issue introduced in commit f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of the security impact of this only came in commit 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP"), which actually omitted flushes for the removal of present PTEs, not just for the removal of empty page tables. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2022-48991? +

CVE-2022-48991 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2022-48991? +

CVE-2022-48991 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2022-48991? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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