CVE-2024-38610

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, thats all I know. Ill 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) Were 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 lets check for ACRN_MEM_ACCESS_WRITE for now.

(2) Were not rejecting refcounted pages.

As we are not using MMU notifiers, messing with refcounted pages is dangerous and can result in use-after-free. Lets 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. Lets loop over all involved PTEs and make sure the PFN range is actually contiguous. Reject everything else: it couldnt have worked either way, and rather made use access PFNs we shouldnt be accessing.

Affected Software

References

• https://git.kernel.org/stable/c/2c8d6e24930b8ef7d4a81787627c559ae0e0d3bb
• https://git.kernel.org/stable/c/3d6586008f7b638f91f3332602592caa8b00b559
• https://git.kernel.org/stable/c/4c4ba3cf3a15ccfbaf787d0296fa42cdb00da9b4
• https://git.kernel.org/stable/c/5c6705aa47b5b78d7ad36fea832bb69caa5bf49a
• https://git.kernel.org/stable/c/afeb0e69627695f759fc73c39c1640dbf8649b32
• https://git.kernel.org/stable/c/e873f36ec890bece26ecce850e969917bceebbb6