CVE-2026-64210: net/mlx5e: xsk: Fix unlocked writing to ICOSQ
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) mlx5etriggerirq() is called while mlx5exskallocrxmpwqe() is running from a different CPU due to affinity change. This can happen because IRQ triggering is done after napicompletedone(). 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) ------------------------------- -------------------------------- napicompletedone() clears SCHED mlx5ecqarm(...) napischeduleprep() sets SCHED mlx5enapipoll() mlx5exskallocrxmpwqe() mlx5eicosqsynclock() // noop memcpy 640 B UMR body advance sq->pc by 10 mlx5etriggerirq(&c->icosq) wqeinfo[pi] = {NOP, 1} mlx5epostnop() advances sq->pc
B) mlx5etriggerirq() is called on the ICOSQ when mlx5etriggernapiicosq() 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/enrx.c:826 [...] [...] Call Trace: <IRQ> mlx5enapipoll+0x11d/0x7f0 [mlx5core] napipoll+0x30/0x200 ? skbdeferfreeflush+0x9c/0xc0 netrxaction+0x2fe/0x3f0 handlesoftirqs+0xd8/0x340 irqexitrcu+0xbc/0xe0 commoninterrupt+0x85/0xa0 </IRQ> <TASK> asmcommoninterrupt+0x26/0x40 [...] ---[ end trace 0000000000000000 ]--- mlx5core 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 mlx5core 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
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Kick the async ICOSQ (instead of locking the ICOSQ) to resolve the race where IRQ triggering on the ICOSQ is done unprotected when NAPI is scheduled on a different CPU due to affinity changes.
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
Systems using the Linux kernel mlx5e XSK path with Mellanox mlx5_core networking are implicated. The race occurs when NAPI affinity changes while XSK work remains and ICOSQ interrupt triggering overlaps work on another CPU.
Does exploitation require authentication or user interaction?
The supplied severity vector indicates network attack vector, low attack complexity, no privileges required, and no user interaction. The available data does not describe a specific exploit method or external trigger.
What is the impact of a successful exploit?
The supplied severity vector indicates high availability impact, with no confidentiality or integrity impact. The underlying issue is an unprotected concurrent write to the ICOSQ.
How can I determine whether a fix is available?
The vulnerability is described as resolved in the Linux kernel. The provided stable-kernel references identify fixes at commits 8d3b91e7d81000d295cd914d4d9d6f860252e2bf and c326f9c68921e2f14dfcecb2f6b4216313d50248.