[PATCH] PCI/AER: increments pci bus reference count in aer-inject process
From: Xiongfeng Wang
Date: Sat Jan 11 2020 - 05:39:53 EST
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.
This patch export pci_bus_get() and pci_bus_put() again and reverts the
following two commits.
fae6b93b19b4 ("PCI: Unexport pci_bus_get() and pci_bus_put()")
ecd29c1a38af ("PCI: Make pci_bus_get(), pci_bus_put() private")
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
---
drivers/pci/bus.c | 2 ++
drivers/pci/pci.h | 2 --
drivers/pci/pcie/aer_inject.c | 8 ++++++++
include/linux/pci.h | 2 ++
4 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 8e40b3e..495059d 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -417,9 +417,11 @@ struct pci_bus *pci_bus_get(struct pci_bus *bus)
get_device(&bus->dev);
return bus;
}
+EXPORT_SYMBOL(pci_bus_get);
void pci_bus_put(struct pci_bus *bus)
{
if (bus)
put_device(&bus->dev);
}
+EXPORT_SYMBOL(pci_bus_put);
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index a0a53bd..cf849b7 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -286,8 +286,6 @@ void __pci_bus_assign_resources(const struct pci_bus *bus,
void pci_reassigndev_resource_alignment(struct pci_dev *dev);
void pci_disable_bridge_window(struct pci_dev *dev);
-struct pci_bus *pci_bus_get(struct pci_bus *bus);
-void pci_bus_put(struct pci_bus *bus);
/* PCIe link information */
#define PCIE_SPEED2STR(speed) \
diff --git a/drivers/pci/pcie/aer_inject.c b/drivers/pci/pcie/aer_inject.c
index 6988fe7..0b6b3d0 100644
--- a/drivers/pci/pcie/aer_inject.c
+++ b/drivers/pci/pcie/aer_inject.c
@@ -307,6 +307,13 @@ static int pci_bus_set_aer_ops(struct pci_bus *bus)
spin_lock_irqsave(&inject_lock, flags);
if (ops == &aer_inj_pci_ops)
goto out;
+ /*
+ * increments the reference count of the pci bus. Otherwise, when we
+ * restore the 'pci_ops' in 'aer_inject_exit', the 'pci_bus' may have
+ * been freed.
+ */
+ pci_bus_get(bus);
+
pci_bus_ops_init(bus_ops, bus, ops);
list_add(&bus_ops->list, &pci_bus_ops_list);
bus_ops = NULL;
@@ -529,6 +536,7 @@ static void __exit aer_inject_exit(void)
while ((bus_ops = pci_bus_ops_pop())) {
pci_bus_set_ops(bus_ops->bus, bus_ops->ops);
+ pci_bus_put(bus_ops->bus);
kfree(bus_ops);
}
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c393dff..adef0da 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1288,6 +1288,8 @@ int pci_add_ext_cap_save_buffer(struct pci_dev *dev,
void pci_release_selected_regions(struct pci_dev *, int);
/* drivers/pci/bus.c */
+struct pci_bus *pci_bus_get(struct pci_bus *bus);
+void pci_bus_put(struct pci_bus *bus);
void pci_add_resource(struct list_head *resources, struct resource *res);
void pci_add_resource_offset(struct list_head *resources, struct resource *res,
resource_size_t offset);
--
1.7.12.4