CVE-2026-68347: iommu/amd: Fix IRQ unsafe locking in gdom allocation

From: Greg Kroah-Hartman <[email protected]>

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

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

iommu/amd: Fix IRQ unsafe locking in gdom allocation

Lockdep complains:

  [  259.410489] =====================================================
  [  259.417287] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
  [  259.424667] 7.0.0-g51db1d8d2113 #54 Not tainted
  [  259.429718] -----------------------------------------------------
  [  259.436516] qemu-system-x86/10143 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
  [  259.444670] ff3b2b1c60305170 (&xa->xa_lock#25){+.+.}-{3:3}, at: __domain_flush_pages+0x17c/0x4b0
  [  259.454485]
                 and this task is already holding:
  [  259.460991] ff3b2b1c98504cc0 (&domain->lock){-.-.}-{3:3}, at: amd_iommu_iotlb_sync+0x25/0x60
  [  259.470408] which would create a new lock dependency:
  [  259.476041]  (&domain->lock){-.-.}-{3:3} -> (&xa->xa_lock#25){+.+.}-{3:3}
  [  259.483615]
                 but this new dependency connects a HARDIRQ-irq-safe lock:
  [  259.492447]  (&domain->lock){-.-.}-{3:3}
  [  259.492449]
                 ... which became HARDIRQ-irq-safe at:
  [  259.503705]   lock_acquire+0xb6/0x2e0
  [  259.507790]   _raw_spin_lock_irqsave+0x3e/0x60
  [  259.512748]   amd_iommu_flush_iotlb_all+0x20/0x50
  [  259.517996]   iommu_dma_free_iova.isra.0+0x1b8/0x1e0
  [  259.523534]   __iommu_dma_unmap+0xc2/0x140
  [  259.528100]   iommu_dma_unmap_phys+0x55/0xc0
  [  259.532863]   dma_unmap_phys+0x274/0x2e0
  [  259.537238]   dma_unmap_page_attrs+0x17/0x30
  [  259.542000]   nvme_unmap_data+0x13e/0x280
  [  259.546473]   nvme_pci_complete_batch+0x45/0x70
  [  259.551524]   nvme_irq+0x83/0x90
  [  259.555123]   __handle_irq_event_percpu+0x92/0x360
  [  259.560466]   handle_irq_event+0x39/0x80
  [  259.564841]   handle_edge_irq+0xb2/0x1a0
  [  259.569214]   __common_interrupt+0x4e/0x130
  [  259.573882]   common_interrupt+0x88/0xa0
  [  259.578256]   asm_common_interrupt+0x27/0x40
  [  259.583019]   cpuidle_enter_state+0x119/0x5d0
  [  259.587877]   cpuidle_enter+0x2e/0x50
  [  259.591962]   do_idle+0x153/0x2c0
  [  259.595657]   cpu_startup_entry+0x29/0x30
  [  259.600128]   start_secondary+0x118/0x150
  [  259.604601]   common_startup_64+0x13e/0x141
  [  259.609266]
                 to a HARDIRQ-irq-unsafe lock:
  [  259.615384]  (&xa->xa_lock#25){+.+.}-{3:3}
  [  259.615386]
                 ... which became HARDIRQ-irq-unsafe at:
  [  259.627039] ...
  [  259.627039]   lock_acquire+0xb6/0x2e0
  [  259.633071]   _raw_spin_lock+0x2f/0x50
  [  259.637250]   amd_iommu_alloc_domain_nested+0x140/0x3c0
  [  259.643078]   iommufd_hwpt_alloc+0x272/0x800 [iommufd]
  [  259.648813]   iommufd_fops_ioctl+0x14e/0x200 [iommufd]
  [  259.654547]   __x64_sys_ioctl+0x9d/0xf0
  ...

Since amd_iommu_domain_flush_pages() necessarily holds domain->lock to do the
flush, switch the allocation side in gdom_info_load_or_alloc_locked() to
HARDIRQ-safe allocation. The IOMMU_DESTROY->free path has the same issue,
so switch that path to HARDIRQ-safe locking as well.

The Linux kernel CVE team has assigned CVE-2026-68347 to this issue.


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

	Issue introduced in 7.0 with commit 757d2b1fdf5b7d6eead5963a49b5780617987ab8 and fixed in 7.1.6 with commit e0c78cdf35af3ada05f9309f4641e9f83c945dbd
	Issue introduced in 7.0 with commit 757d2b1fdf5b7d6eead5963a49b5780617987ab8 and fixed in 7.2-rc5 with commit 0db3a430d9681fdb29890bef6934cd89cd1745d0

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-2026-68347
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/iommu/amd/nested.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/e0c78cdf35af3ada05f9309f4641e9f83c945dbd
	https://git.kernel.org/stable/c/0db3a430d9681fdb29890bef6934cd89cd1745d0