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

iommu/vt-d: Fix WARN_ON in iommu probe path

Commit 1a75cc710b95 (“iommu/vt-d: Use rbtree to track iommu probed
devices”) adds all devices probed by the iommu driver in a rbtree
indexed by the source ID of each device. It assumes that each device
has a unique source ID. This assumption is incorrect and the VT-d
spec doesn’t state this requirement either.

The reason for using a rbtree to track devices is to look up the device
with PCI bus and devfunc in the paths of handling ATS invalidation time
out error and the PRI I/O page faults. Both are PCI ATS feature related.

Only track the devices that have PCI ATS capabilities in the rbtree to
avoid unnecessary WARN_ON in the iommu probe path. Otherwise, on some
platforms below kernel splat will be displayed and the iommu probe results
in failure.

WARNING: CPU: 3 PID: 166 at drivers/iommu/intel/iommu.c:158 intel_iommu_probe_device+0x319/0xd90
Call Trace:
<TASK>
? __warn+0x7e/0x180
? intel_iommu_probe_device+0x319/0xd90
? report_bug+0x1f8/0x200
? handle_bug+0x3c/0x70
? exc_invalid_op+0x18/0x70
? asm_exc_invalid_op+0x1a/0x20
? intel_iommu_probe_device+0x319/0xd90
? debug_mutex_init+0x37/0x50
__iommu_probe_device+0xf2/0x4f0
iommu_probe_device+0x22/0x70
iommu_bus_notifier+0x1e/0x40
notifier_call_chain+0x46/0x150
blocking_notifier_call_chain+0x42/0x60
bus_notify+0x2f/0x50
device_add+0x5ed/0x7e0
platform_device_add+0xf5/0x240
mfd_add_devices+0x3f9/0x500
? preempt_count_add+0x4c/0xa0
? up_write+0xa2/0x1b0
? __debugfs_create_file+0xe3/0x150
intel_lpss_probe+0x49f/0x5b0
? pci_conf1_write+0xa3/0xf0
intel_lpss_pci_probe+0xcf/0x110 [intel_lpss_pci]
pci_device_probe+0x95/0x120
really_probe+0xd9/0x370
? pfx_driver_attach+0x10/0x10
__driver_probe_device+0x73/0x150
driver_probe_device+0x19/0xa0
__driver_attach+0xb6/0x180
? pfx_driver_attach+0x10/0x10
bus_for_each_dev+0x77/0xd0
bus_add_driver+0x114/0x210
driver_register+0x5b/0x110
? __pfx_intel_lpss_pci_driver_init+0x10/0x10 [intel_lpss_pci]
do_one_initcall+0x57/0x2b0
? kmalloc_trace+0x21e/0x280
? do_init_module+0x1e/0x210
do_init_module+0x5f/0x210
load_module+0x1d37/0x1fc0
? init_module_from_file+0x86/0xd0
init_module_from_file+0x86/0xd0
idempotent_init_module+0x17c/0x230
__x64_sys_finit_module+0x56/0xb0
do_syscall_64+0x6e/0x140
entry_SYSCALL_64_after_hwframe+0x71/0x79