CVE-2022-48797 mm: don't try to NUMA-migrate COW pages that have other uses

What is CVE-2022-48797?

CVE-2022-48797 is a high-severity memory corruption vulnerability in Linux kernel, published on 16 Jul 2024. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

mm: don't try to NUMA-migrate COW pages that have other uses

Oded Gabbay reports that enabling NUMA balancing causes corruption with his Gaudi accelerator test load:

"All the details are in the bug, but the bottom line is that somehow, this patch causes corruption when the numa balancing feature is enabled AND we don't use process affinity AND we use GUP to pin pages so our accelerator can DMA to/from system memory.

Either disabling numa balancing, using process affinity to bind to specific numa-node or reverting this patch causes the bug to disappear"

and Oded bisected the issue to commit 09854ba94c6a ("mm: do_wp_page() simplification").

Now, the NUMA balancing shouldn't actually be changing the writability of a page, and as such shouldn't matter for COW. But it appears it does. Suspicious.

However, regardless of that, the condition for enabling NUMA faults in change_pte_range() is nonsensical. It uses "page_mapcount(page)" to decide if a COW page should be NUMA-protected or not, and that makes absolutely no sense.

The number of mappings a page has is irrelevant: not only does GUP get a reference to a page as in Oded's case, but the other mappings migth be paged out and the only reference to them would be in the page count.

Since we should never try to NUMA-balance a page that we can't move anyway due to other references, just fix the code to use 'page_count()'. Oded confirms that that fixes his issue.

Now, this does imply that something in NUMA balancing ends up changing page protections (other than the obvious one of making the page inaccessible to get the NUMA faulting information). Otherwise the COW simplification wouldn't matter - since doing the GUP on the page would make sure it's writable.

The cause of that permission change would be good to figure out too, since it clearly results in spurious COW events - but fixing the nonsensical test that just happened to work before is obviously the CorrectThing(tm) to do regardless.

Which versions are affected by CVE-2022-48797?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2022-48797?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2022-48797 being exploited?

There is no known exploitation of CVE-2022-48797 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2022-48797, GHSA-8ccr-7w7q-vmr3, UBUNTU-CVE-2022-48797.