CVE-2026-23134

/// Technical 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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References