CVE-2026-46029

/// Technical description

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

mm/slab: return NULL early from kmalloc_nolock() in NMI on UP

On UP kernels (!CONFIG_SMP), spin_trylock() is a no-op that

unconditionally succeeds even when the lock is already held. As a

result, kmalloc_nolock() called from NMI context can re-enter the slab

allocator and acquire n->list_lock that the interrupted context is

already holding, corrupting slab state.

With CONFIG_DEBUG_SPINLOCK on UP, the following BUG is triggered with

the slub_kunit test module:

BUG: spinlock trylock failure on UP on CPU#0, kunit_try_catch/243

[...]

Call Trace:

<NMI>

dump_stack_lvl+0x3f/0x60

do_raw_spin_trylock+0x41/0x50

_raw_spin_trylock+0x24/0x50

get_from_partial_node+0x120/0x4d0

___slab_alloc+0x8a/0x4c0

kmalloc_nolock_noprof+0x164/0x310

[...]

</NMI>

Fix this by returning NULL early when invoked from NMI on a UP kernel.

/// 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