CVE-2026-97943

Status: UPDATED  |  Advisory ID: CVE-2026-97943

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

x86/mm/pat: Acquire init_mm write lock on collapse to avoid UAF

x86 implements page attribute modification using its Change Page

Attributes (CPA) mechanism.

This tracks properties of ranges such as cache mode through x86 page

attributes, and as part of that logic manipulates kernel page tables.

Since commit:

41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation")

ranges of kernel page table entries can be collapsed into

huge page table entries as part of this logic.

As part of this collapse, it frees the page tables which the collapsed

entries previously pointed to, and it does so without any relevant locks

being held to preclude concurrent kernel page table walkers.

The only way this code can be reached is if CPA_COLLAPSE is specified, and

this is only set in set_memory_rox() via:

set_memory_rox()

-> change_page_attr_set_clr()

-> cpa_flush()

-> cpa_collapse_large_pages()

Notable users of this are execmem and BPF when manipulating executable

mappings.

However, this is problematic for ptdump as it walks ranges it does not own

and thus runs the risk of a use-after-free on page tables freed underneath

it.

In addition, concurrent CPA collapse operations are possible which can also

cause races.

Resolve the issue by acquiring the mmap write lock on init_mm across the

whole operation.

It is safe to acquire a sleeping lock as all the callers invoke

set_memory_rox() from process context and in any case,

change_page_attr_set_clr() calls vm_unmap_alias() which ultimately takes a

mutex, disallowing atomic context here. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References