Subject: CVE-2024-35957: iommu/vt-d: Fix WARN_ON in iommu probe path

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

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

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

The Linux kernel CVE team has assigned CVE-2024-35957 to this issue.

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

	Issue introduced in 6.8.2 with commit c618d446f1d6 and fixed in 6.8.7 with commit fba8ca3e6f60

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-2024-35957
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/intel/iommu.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/fba8ca3e6f608b92e54271fdbd3ce569361939fc
	https://git.kernel.org/stable/c/89436f4f54125b1297aec1f466efd8acb4ec613d