CVE-2026-64210: net/mlx5e: xsk: Fix unlocked writing to ICOSQ

CVE-2026-64210: net/mlx5e: xsk: Fix unlocked writing to ICOSQ

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

The Linux kernel CVE team has assigned CVE-2026-64210 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.3 with commit db05815b36cbd486c86fd002dfa81c9af6245e25 and fixed in 7.0.11 with commit 8d3b91e7d81000d295cd914d4d9d6f860252e2bf
	Issue introduced in 5.3 with commit db05815b36cbd486c86fd002dfa81c9af6245e25 and fixed in 7.1 with commit c326f9c68921e2f14dfcecb2f6b4216313d50248

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-64210
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/8d3b91e7d81000d295cd914d4d9d6f860252e2bf
	https://git.kernel.org/stable/c/c326f9c68921e2f14dfcecb2f6b4216313d50248