CVE-2026-46035

Summary

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

mm/page_alloc: return NULL early from alloc_frozen_pages_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, alloc_frozen_pages_nolock() called from NMI context can re-enter rmqueue() and acquire the zone lock that the interrupted context is already holding, corrupting the freelists.

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 rmqueue.isra.0+0x2a9/0xa70 get_page_from_freelist+0xeb/0x450 alloc_frozen_pages_nolock_noprof+0x111/0x1e0 allocate_slab+0x42a/0x500 ___slab_alloc+0xa7/0x4c0 kmalloc_nolock_noprof+0x164/0x310 […] </NMI>

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

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/05b4ed8bef30bba4f559c8d835e2dd20c48cf8a4
• https://git.kernel.org/stable/c/a6d57efeaae3f3b3656514f600eac96be713d90e
• https://git.kernel.org/stable/c/620b46ed6ae17c8438d889c8c0cfddab36a1476c

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