drivers/virt/acrn: fix PFNMAP PTE checks in acrn_vm_ram_map()

Summary

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.

Timeline

1. Jun 19, 2024, 1:56 PM UTCCVE published
2. Jun 24, 2024, 6:14 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Aug 5, 2026, 11:33 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 5.15.33 · fixed in 5.15.161; From 5.16.19 · fixed in 5.17; From 5.17.2 · fixed in 5.18

• Linux Linux

  5.18

References 6