CVE-2026-43466: net/mlx5e: Fix DMA FIFO desync on error CQE SQ recovery

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

net/mlx5e: Fix DMA FIFO desync on error CQE SQ recovery

In case of a TX error CQE, a recovery flow is triggered,
mlx5e_reset_txqsq_cc_pc() resets dma_fifo_cc to 0 but not dma_fifo_pc,
desyncing the DMA FIFO producer and consumer.

After recovery, the producer pushes new DMA entries at the old
dma_fifo_pc, while the consumer reads from position 0.
This causes us to unmap stale DMA addresses from before the recovery.

The DMA FIFO is a purely software construct with no HW counterpart.
At the point of reset, all WQEs have been flushed so dma_fifo_cc is
already equal to dma_fifo_pc. There is no need to reset either counter,
similar to how skb_fifo pc/cc are untouched.

Remove the 'dma_fifo_cc = 0' reset.

This fixes the following WARNING:
    WARNING: CPU: 0 PID: 0 at drivers/iommu/dma-iommu.c:1240 iommu_dma_unmap_page+0x79/0x90
    Modules linked in: mlx5_vdpa vringh vdpa bonding mlx5_ib mlx5_vfio_pci ipip mlx5_fwctl tunnel4 mlx5_core ib_ipoib geneve ip6_gre ip_gre gre nf_tables ip6_tunnel rdma_ucm ib_uverbs ib_umad vfio_pci vfio_pci_core act_mirred act_skbedit act_vlan vhost_net vhost tap ip6table_mangle ip6table_nat ip6table_filter ip6_tables iptable_mangle cls_matchall nfnetlink_cttimeout act_gact cls_flower sch_ingress vhost_iotlb iptable_raw tunnel6 vfio_iommu_type1 vfio openvswitch nsh rpcsec_gss_krb5 auth_rpcgss oid_registry xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink iptable_nat nf_nat xt_addrtype br_netfilter overlay zram zsmalloc rpcrdma ib_iser libiscsi scsi_transport_iscsi rdma_cm iw_cm ib_cm ib_core fuse [last unloaded: nf_tables]
    CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.13.0-rc5_for_upstream_min_debug_2024_12_30_21_33 #1
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
    RIP: 0010:iommu_dma_unmap_page+0x79/0x90
    Code: 2b 4d 3b 21 72 26 4d 3b 61 08 73 20 49 89 d8 44 89 f9 5b 4c 89 f2 4c 89 e6 48 89 ef 5d 41 5c 41 5d 41 5e 41 5f e9 c7 ae 9e ff <0f> 0b 5b 5d 41 5c 41 5d 41 5e 41 5f c3 66 2e 0f 1f 84 00 00 00 00
    Call Trace:
     <IRQ>
     ? __warn+0x7d/0x110
     ? iommu_dma_unmap_page+0x79/0x90
     ? report_bug+0x16d/0x180
     ? handle_bug+0x4f/0x90
     ? exc_invalid_op+0x14/0x70
     ? asm_exc_invalid_op+0x16/0x20
     ? iommu_dma_unmap_page+0x79/0x90
     ? iommu_dma_unmap_page+0x2e/0x90
     dma_unmap_page_attrs+0x10d/0x1b0
     mlx5e_tx_wi_dma_unmap+0xbe/0x120 [mlx5_core]
     mlx5e_poll_tx_cq+0x16d/0x690 [mlx5_core]
     mlx5e_napi_poll+0x8b/0xac0 [mlx5_core]
     __napi_poll+0x24/0x190
     net_rx_action+0x32a/0x3b0
     ? mlx5_eq_comp_int+0x7e/0x270 [mlx5_core]
     ? notifier_call_chain+0x35/0xa0
     handle_softirqs+0xc9/0x270
     irq_exit_rcu+0x71/0xd0
     common_interrupt+0x7f/0xa0
     </IRQ>
     <TASK>
     asm_common_interrupt+0x22/0x40

The Linux kernel CVE team has assigned CVE-2026-43466 to this issue.


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

	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 5.10.253 with commit 821f85d619f7f22cda7b9d7de89cf5eeb1d11544
	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 5.15.203 with commit 6eb68ecc5acc3b319986566c595990b8a7265b23
	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 6.1.167 with commit 6f41f7812bfa7f991b732a4b45c5c52fc4be3b4e
	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 6.6.130 with commit 383b37c04a4827ba60b2bafc1a6cdfd995aed58f
	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 6.12.78 with commit 9c5ee9b981ee050b73fdf3f4a2464d6f1a8e10a8
	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 6.18.19 with commit ce1b19dd0684eeb68a124c11085bd611260b36d9
	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 6.19.9 with commit 829efcccfa8f69db5dc8332961295587d218cee6
	Issue introduced in 4.17 with commit db75373c91b0cfb6a68ad6ae88721e4e21ae6261 and fixed in 7.0 with commit 1633111d69053512d099658d4a05fc736fab36b0

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-2026-43466
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/reporter_tx.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/821f85d619f7f22cda7b9d7de89cf5eeb1d11544
	https://git.kernel.org/stable/c/6eb68ecc5acc3b319986566c595990b8a7265b23
	https://git.kernel.org/stable/c/6f41f7812bfa7f991b732a4b45c5c52fc4be3b4e
	https://git.kernel.org/stable/c/383b37c04a4827ba60b2bafc1a6cdfd995aed58f
	https://git.kernel.org/stable/c/9c5ee9b981ee050b73fdf3f4a2464d6f1a8e10a8
	https://git.kernel.org/stable/c/ce1b19dd0684eeb68a124c11085bd611260b36d9
	https://git.kernel.org/stable/c/829efcccfa8f69db5dc8332961295587d218cee6
	https://git.kernel.org/stable/c/1633111d69053512d099658d4a05fc736fab36b0