PCI/AER: increments pci bus reference count in aer-inject process

hulk inclusion
category: bugfix
bugzilla: 28335
CVE: NA

-------------------------------------------------

When I test 'aer-inject' with the following procedures:
1. inject a fatal error into a PCI device
2. remove the parent device by sysfs
3. execute command 'rmmod aer-inject'

I came across the following use-after-free.

[  297.581524] ==================================================================
[  297.581543] BUG: KASAN: use-after-free in pci_bus_set_ops+0xb4/0xb8
[  297.581545] Read of size 8 at addr ffff802edbde80e0 by task rmmod/21839

[  297.581552] CPU: 119 PID: 21839 Comm: rmmod Kdump: loaded Not tainted 4.19.36 #1
[  297.581554] Hardware name: Huawei TaiShan 2280 V2/BC82AMDD, BIOS 1.05 09/18/2019
[  297.581556] Call trace:
[  297.581561]  dump_backtrace+0x0/0x360
[  297.581563]  show_stack+0x24/0x30
[  297.581569]  dump_stack+0xd8/0x104
[  297.581576]  print_address_description+0x68/0x278
[  297.581578]  kasan_report+0x204/0x330
[  297.581580]  __asan_report_load8_noabort+0x30/0x40
[  297.581582]  pci_bus_set_ops+0xb4/0xb8
[  297.581591]  aer_inject_exit+0x198/0x334 [aer_inject]
[  297.581595]  __arm64_sys_delete_module+0x310/0x490
[  297.581601]  el0_svc_common+0xfc/0x278
[  297.581603]  el0_svc_handler+0x50/0xc0
[  297.581605]  el0_svc+0x8/0xc

[  297.581608] Allocated by task 1:
[  297.581611]  kasan_kmalloc+0xe0/0x190
[  297.581614]  kmem_cache_alloc_trace+0x104/0x218
[  297.581616]  pci_alloc_bus+0x50/0x2e0
[  297.581618]  pci_add_new_bus+0xa8/0xe08
[  297.581620]  pci_scan_bridge_extend+0x884/0xb28
[  297.581623]  pci_scan_child_bus_extend+0x350/0x628
[  297.581625]  pci_scan_child_bus+0x24/0x30
[  297.581627]  pci_scan_bridge_extend+0x3b8/0xb28
[  297.581629]  pci_scan_child_bus_extend+0x350/0x628
[  297.581631]  pci_scan_child_bus+0x24/0x30
[  297.581635]  acpi_pci_root_create+0x558/0x888
[  297.581640]  pci_acpi_scan_root+0x198/0x330
[  297.581641]  acpi_pci_root_add+0x7bc/0xbb0
[  297.581646]  acpi_bus_attach+0x2f4/0x728
[  297.581647]  acpi_bus_attach+0x1b0/0x728
[  297.581649]  acpi_bus_attach+0x1b0/0x728
[  297.581651]  acpi_bus_scan+0xa0/0x110
[  297.581657]  acpi_scan_init+0x20c/0x500
[  297.581659]  acpi_init+0x54c/0x5d4
[  297.581661]  do_one_initcall+0xbc/0x480
[  297.581665]  kernel_init_freeable+0x5fc/0x6ac
[  297.581670]  kernel_init+0x18/0x128
[  297.581671]  ret_from_fork+0x10/0x18

[  297.581673] Freed by task 19270:
[  297.581675]  __kasan_slab_free+0x120/0x228
[  297.581677]  kasan_slab_free+0x10/0x18
[  297.581678]  kfree+0x80/0x1f8
[  297.581680]  release_pcibus_dev+0x54/0x68
[  297.581686]  device_release+0xd4/0x1c0
[  297.581689]  kobject_put+0x12c/0x400
[  297.581691]  device_unregister+0x30/0xc0
[  297.581693]  pci_remove_bus+0xe8/0x1c0
[  297.581695]  pci_remove_bus_device+0xd0/0x2f0
[  297.581697]  pci_stop_and_remove_bus_device_locked+0x2c/0x40
[  297.581701]  remove_store+0x1b8/0x1d0
[  297.581703]  dev_attr_store+0x60/0x80
[  297.581708]  sysfs_kf_write+0x104/0x170
[  297.581710]  kernfs_fop_write+0x23c/0x430
[  297.581713]  __vfs_write+0xec/0x4e0
[  297.581714]  vfs_write+0x12c/0x3d0
[  297.581715]  ksys_write+0xd0/0x190
[  297.581716]  __arm64_sys_write+0x70/0xa0
[  297.581718]  el0_svc_common+0xfc/0x278
[  297.581720]  el0_svc_handler+0x50/0xc0
[  297.581721]  el0_svc+0x8/0xc

[  297.581724] The buggy address belongs to the object at ffff802edbde8000
                which belongs to the cache kmalloc-2048 of size 2048
[  297.581726] The buggy address is located 224 bytes inside of
                2048-byte region [ffff802edbde8000, ffff802edbde8800)
[  297.581727] The buggy address belongs to the page:
[  297.581730] page:ffff7e00bb6f7a00 count:1 mapcount:0 mapping:ffff8026de810780 index:0x0 compound_mapcount: 0
[  297.591520] flags: 0x2ffffe0000008100(slab|head)
[  297.596121] raw: 2ffffe0000008100 ffff7e00bb6f5008 ffff7e00bb6ff608 ffff8026de810780
[  297.596123] raw: 0000000000000000 00000000000f000f 00000001ffffffff 0000000000000000
[  297.596124] page dumped because: kasan: bad access detected

[  297.596126] Memory state around the buggy address:
[  297.596128]  ffff802edbde7f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  297.596129]  ffff802edbde8000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  297.596131] >ffff802edbde8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  297.596132]                                                        ^
[  297.596133]  ffff802edbde8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  297.596135]  ffff802edbde8180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  297.596135] ==================================================================

It is because when we unload the module and restore the member 'pci_ops'
of 'pci_bus', the 'pci_bus' has been freed. This patch increments the
reference count of 'pci_bus' when we modify its member 'pci_ops' and
decrements the reference count after we have restored its member.

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>