CVE-2026-64210

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

net/mlx5e: xsk: Fix unlocked writing to ICOSQ

During napi poll, when the affinity changes and there's still XSK work

to be done, we trigger an ICOSQ interrupt on the new CPU. However, this

triggering on the ICOSQ is done unprotected.

There are 2 such races:

A) mlx5e_trigger_irq() is called while mlx5e_xsk_alloc_rx_mpwqe() is

running from a different CPU due to affinity change. This can happen

because IRQ triggering is done after napi_complete_done(). At this point

the NAPI can be scheduled on a different CPU. Like this:

CPU A (old affinity, NAPI tail) CPU B (new affinity, fresh NAPI)

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

napi_complete_done() clears SCHED

mlx5e_cq_arm(...)

napi_schedule_prep() sets SCHED

mlx5e_napi_poll()

mlx5e_xsk_alloc_rx_mpwqe()

mlx5e_icosq_sync_lock() // noop

memcpy 640 B UMR body

advance sq->pc by 10

mlx5e_trigger_irq(&c->icosq)

wqe_info[pi] = {NOP, 1}

mlx5e_post_nop() advances sq->pc

B) mlx5e_trigger_irq() is called on the ICOSQ when

mlx5e_trigger_napi_icosq() is running.

The obvious fix would be to lock the ICOSQ. But ICOSQ has an optimized

locking scheme that doesn't work for this scenario. Kick the async ICOSQ

instead which is always locked.

This issue was noticed in the wild with the following splat:

netdevice: ge-0-0-1: Bad OP in ICOSQ CQE: 0xd

WARNING: drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:826 [...]

[...]

Call Trace:

<IRQ>

mlx5e_napi_poll+0x11d/0x7f0 [mlx5_core]

__napi_poll+0x30/0x200

? skb_defer_free_flush+0x9c/0xc0

net_rx_action+0x2fe/0x3f0

handle_softirqs+0xd8/0x340

__irq_exit_rcu+0xbc/0xe0

common_interrupt+0x85/0xa0

</IRQ>

<TASK>

asm_common_interrupt+0x26/0x40

[...]

---[ end trace 0000000000000000 ]---

mlx5_core 0000:08:00.0 ge-0-0-1: Error cqe on cqn 0x548, ci 0x2022, qn 0x8f4,

opcode 0xd, syndrome 0x2, vendor syndrome 0x68

00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00000030: 00 00 00 00 01 00 68 02 01 00 08 f4 de 14 59 d2

WQE DUMP: WQ size 16384 WQ cur size 0, WQE index 0x1e14, len: 64

00000000: 00 00 00 01 d9 ed 80 02 00 00 00 01 d9 ed 90 02

00000010: 00 00 00 01 d9 ed a0 02 00 00 00 01 d9 ed b0 02

00000020: 00 00 00 01 d9 ed c0 02 00 00 00 01 d9 ed d0 02

00000030: 00 00 00 01 d9 ed e0 02 00 00 00 01 d9 ed f0 02

mlx5_core 0000:08:00.0 ge-0-0-1: Error cqe on cqn 0x548, ci 0x2023, qn 0x8f4,

opcode 0xd, syndrome 0x5, vendor syndrome 0xf9

00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00000030: 00 00 00 00 01 00 f9 05 01 00 08 f4 de 15 cf d2