CVE-2026-90046: mm/page_alloc: don't spin_trylock() in NMI on UP
In the Linux kernel, the following vulnerability has been resolved:
mm/pagealloc: don't spintrylock() in NMI on UP
Patch series "mm/pagealloc: fixes for freepagesnolock() on RT/UP".
Pre-existing bugs found by Sashiko during review of this other series: https://lore.kernel.org/all/20260703-alloc-trylock-v5-0-c87b714e19d3@google.com/
I have not reproduced these bugs, and I suspect there is no real-world user that is affected by them.
This patch (of 2):
As noted in canspintrylock(), using this is unsafe in this context. commit 620b46ed6ae17 ("mm/pagealloc: return NULL early from allocfrozenpagesnolock() in NMI on UP") fixed this on the alloc side but missed the free side.
Impact: If BPF programs using these features in NMI (probably tracing) are present on non-SMP builds this might crash the kernel and is probably exploitable by local attackers for privilege escalation.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Patch 620b46ed6ae17
Event History
Frequently Asked Questions
Which systems are realistically exposed to this issue?
The described exposure is limited to non-SMP (uniprocessor) Linux kernel builds that have BPF programs using the affected features from NMI context, probably tracing-related programs. The report notes that there may be no real-world users affected.
What would an attacker need to exploit it?
A local attacker would need a system with the affected NMI-context BPF usage on a non-SMP build. Under those conditions, the issue might crash the kernel and is described as probably exploitable for local privilege escalation.
Are typical SMP systems affected?
The stated impact specifically concerns non-SMP builds. The provided information does not identify SMP builds as affected.
What should be prioritized if patching cannot happen immediately?
Prioritize identifying and avoiding BPF programs that use the affected features in NMI context on non-SMP systems, particularly tracing-related use. Systems without that combination are not described as exposed by the available information.