PCI: Fix use-after-free in pci_bus_release_domain_nr()

commit 30ba2d09ed upstream.

Commit c14f7ccc9f ("PCI: Assign PCI domain IDs by ida_alloc()")
introduced a use-after-free bug in the bus removal cleanup. The issue was
found with kfence:

  [   19.293351] BUG: KFENCE: use-after-free read in pci_bus_release_domain_nr+0x10/0x70

  [   19.302817] Use-after-free read at 0x000000007f3b80eb (in kfence-#115):
  [   19.309677]  pci_bus_release_domain_nr+0x10/0x70
  [   19.309691]  dw_pcie_host_deinit+0x28/0x78
  [   19.309702]  tegra_pcie_deinit_controller+0x1c/0x38 [pcie_tegra194]
  [   19.309734]  tegra_pcie_dw_probe+0x648/0xb28 [pcie_tegra194]
  [   19.309752]  platform_probe+0x90/0xd8
  ...

  [   19.311457] kfence-#115: 0x00000000063a155a-0x00000000ba698da8, size=1072, cache=kmalloc-2k

  [   19.311469] allocated by task 96 on cpu 10 at 19.279323s:
  [   19.311562]  __kmem_cache_alloc_node+0x260/0x278
  [   19.311571]  kmalloc_trace+0x24/0x30
  [   19.311580]  pci_alloc_bus+0x24/0xa0
  [   19.311590]  pci_register_host_bridge+0x48/0x4b8
  [   19.311601]  pci_scan_root_bus_bridge+0xc0/0xe8
  [   19.311613]  pci_host_probe+0x18/0xc0
  [   19.311623]  dw_pcie_host_init+0x2c0/0x568
  [   19.311630]  tegra_pcie_dw_probe+0x610/0xb28 [pcie_tegra194]
  [   19.311647]  platform_probe+0x90/0xd8
  ...

  [   19.311782] freed by task 96 on cpu 10 at 19.285833s:
  [   19.311799]  release_pcibus_dev+0x30/0x40
  [   19.311808]  device_release+0x30/0x90
  [   19.311814]  kobject_put+0xa8/0x120
  [   19.311832]  device_unregister+0x20/0x30
  [   19.311839]  pci_remove_bus+0x78/0x88
  [   19.311850]  pci_remove_root_bus+0x5c/0x98
  [   19.311860]  dw_pcie_host_deinit+0x28/0x78
  [   19.311866]  tegra_pcie_deinit_controller+0x1c/0x38 [pcie_tegra194]
  [   19.311883]  tegra_pcie_dw_probe+0x648/0xb28 [pcie_tegra194]
  [   19.311900]  platform_probe+0x90/0xd8
  ...

  [   19.313579] CPU: 10 PID: 96 Comm: kworker/u24:2 Not tainted 6.2.0 #4
  [   19.320171] Hardware name:  /, BIOS 1.0-d7fb19b 08/10/2022
  [   19.325852] Workqueue: events_unbound deferred_probe_work_func

The stack trace is a bit misleading as dw_pcie_host_deinit() doesn't
directly call pci_bus_release_domain_nr(). The issue turns out to be in
pci_remove_root_bus() which first calls pci_remove_bus() which frees the
struct pci_bus when its struct device is released. Then
pci_bus_release_domain_nr() is called and accesses the freed struct
pci_bus. Reordering these fixes the issue.

Fixes: c14f7ccc9f ("PCI: Assign PCI domain IDs by ida_alloc()")
Link: https://lore.kernel.org/r/20230329123835.2724518-1-robh@kernel.org
Link: https://lore.kernel.org/r/b529cb69-0602-9eed-fc02-2f068707a006@nvidia.com
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: stable@vger.kernel.org	# v6.2+
Cc: Pali Rohár <pali@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/pci/remove.c

@@ -157,8 +157,6 @@ void pci_remove_root_bus(struct pci_bus *bus)
 	list_for_each_entry_safe(child, tmp,
 				 &bus->devices, bus_list)
 		pci_remove_bus_device(child);
-	pci_remove_bus(bus);
-	host_bridge->bus = NULL;
 
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
 	/* Release domain_nr if it was dynamically allocated */
@@ -166,6 +164,9 @@ void pci_remove_root_bus(struct pci_bus *bus)
 		pci_bus_release_domain_nr(bus, host_bridge->dev.parent);
 #endif
 
+	pci_remove_bus(bus);
+	host_bridge->bus = NULL;
+
 	/* remove the host bridge */
 	device_del(&host_bridge->dev);
 }