CVE-2022-49077: mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0)

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-26 · updated 2026-06-17
Weakness: CWE-193

Description

In the Linux kernel, the following vulnerability has been resolved: mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0) If an mremap() syscall with old_size=0 ends up in move_page_tables(), it will call invalidate_range_start()/invalidate_range_end() unnecessarily, i.e. with an empty range. This causes a WARN in KVM's mmu_notifier. In the past, empty ranges have been diagnosed to be off-by-one bugs, hence the WARNing. Given the low (so far) number of unique reports, the benefits of detecting more buggy callers seem to outweigh the cost of having to fix cases such as this one, where userspace is doing something silly. In this particular case, an early return from move_page_tables() is enough to fix the issue.

Affected products

Linux kernel: before 4.9.311; from 4.10 before 4.14.276; from 4.15 before 4.19.238; from 4.20 before 5.4.189; from 5.5 before 5.10.111; from 5.11 before 5.15.34 — fixed in 4.14.276, 4.19.238, 4.9.311, 5.10.111, 5.15.34, 5.16.20

How to fix

Upgrade to a fixed version: Linux kernel 4.14.276, 4.19.238, 4.9.311, 5.10.111. Check the vendor advisory for mitigations.

References

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