🛡️ CVE-2026-43285 — kernel

mm/slab: do not access current->mems_allowed_seq if !allow_spin

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

mm/slab: do not access current->mems_allowed_seq if !allow_spin

Lockdep complains when get_from_any_partial() is called in an NMI

context, because current->mems_allowed_seq is seqcount_spinlock_t and

not NMI-safe:

================================

WARNING: inconsistent lock state

6.19.0-rc5-kfree-rcu+ #315 Tainted: G N

--------------------------------

inconsistent {INITIAL USE} -> {IN-NMI} usage.

kunit_try_catch/9989 [HC1[1]:SC0[0]:HE0:SE1] takes:

ffff889085799820 (&____s->seqcount#3){.-.-}-{0:0}, at: ___slab_alloc+0x58f/0xc00

{INITIAL USE} state was registered at:

lock_acquire+0x185/0x320

kernel_init_freeable+0x391/0x1150

kernel_init+0x1f/0x220

ret_from_fork+0x736/0x8f0

ret_from_fork_asm+0x1a/0x30

irq event stamp: 56

hardirqs last enabled at (55): [<ffffffff850a68d7>] _raw_spin_unlock_irq+0x27/0x70

hardirqs last disabled at (56): [<ffffffff850858ca>] __schedule+0x2a8a/0x6630

softirqs last enabled at (0): [<ffffffff81536711>] copy_process+0x1dc1/0x6a10

softirqs last disabled at (0): [<0000000000000000>] 0x0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0

----

lock(&____s->seqcount#3);

<Interrupt>

lock(&____s->seqcount#3);

* DEADLOCK *

According to Documentation/locking/seqlock.rst, seqcount_t is not

NMI-safe and seqcount_latch_t should be used when read path can interrupt

the write-side critical section. In this case, do not access

current->mems_allowed_seq and avoid retry.