CVE-2024-38610: drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-06-19 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map() Patch series "mm: follow_pte() improvements and acrn follow_pte() fixes". Patch #1 fixes a bunch of issues I spotted in the acrn driver. It compiles, that's all I know. I'll appreciate some review and testing from acrn folks. Patch #2+#3 improve follow_pte(), passing a VMA instead of the MM, adding more sanity checks, and improving the documentation. Gave it a quick test on x86-64 using VM_PAT that ends up using follow_pte(). This patch (of 3): We currently miss handling various cases, resulting in a dangerous follow_pte() (previously follow_pfn()) usage. (1) We're not checking PTE write permissions. Maybe we should simply always require pte_write() like we do for pin_user_pages_fast(FOLL_WRITE)? Hard to tell, so let's check for ACRN_MEM_ACCESS_WRITE for now. (2) We're not rejecting refcounted pages. As we are not using MMU notifiers, messing with refcounted pages is dangerous and can result in use-after-free. Let's make sure to reject them. (3) We are only looking at the first PTE of a bigger range. We only lookup a single PTE, but memmap->len may span a larger area. Let's loop over all involved PTEs and make sure the PFN range is actually contiguous. Reject everything else: it couldn't have worked either way, and rather made use access PFNs we shouldn't be accessing.

Affected products

Linux kernel: from 5.15.33 before 5.15.161; from 5.16.19 before 5.17; from 5.17.2 before 6.1.93; from 6.2 before 6.6.33; from 6.7 before 6.8.12; from 6.9 before 6.9.3 — fixed in 5.15.161, 5.17, 6.1.93, 6.6.33, 6.8.12, 6.9.3

How to fix

Upgrade to a fixed version: Linux kernel 5.15.161, 5.17, 6.1.93, 6.6.33. Check the vendor advisory for mitigations.

References

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