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Message-ID: <20210720130400.49153-1-wangxiongfeng2@huawei.com>
Date: Tue, 20 Jul 2021 21:04:00 +0800
From: Xiongfeng Wang <wangxiongfeng2@...wei.com>
To: <bhelgaas@...gle.com>, <keith.busch@...el.com>, <lukas@...ner.de>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<wangxiongfeng2@...wei.com>
Subject: [PATCH] PCI/sysfs: Take reference on device to be removed
When I do some aer-inject and sysfs remove stress tests, I got the
following use-after-free Calltrace:
==================================================================
BUG: KASAN: use-after-free in pci_stop_bus_device+0x174/0x178
Read of size 8 at addr fffffc3e2e402218 by task bash/26311
CPU: 38 PID: 26311 Comm: bash Tainted: G W 4.19.105+ #82
Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V5.B161.01 06/10/2021
Call trace:
dump_backtrace+0x0/0x360
show_stack+0x24/0x30
dump_stack+0x130/0x164
print_address_description+0x68/0x278
kasan_report+0x204/0x330
__asan_report_load8_noabort+0x30/0x40
pci_stop_bus_device+0x174/0x178
pci_stop_and_remove_bus_device_locked+0x24/0x40
remove_store+0x1c8/0x1e0
dev_attr_store+0x60/0x80
sysfs_kf_write+0x104/0x170
kernfs_fop_write+0x23c/0x430
__vfs_write+0xec/0x4e0
vfs_write+0x12c/0x3d0
ksys_write+0xe8/0x208
__arm64_sys_write+0x70/0xa0
el0_svc_common+0x10c/0x450
el0_svc_handler+0x50/0xc0
el0_svc+0x10/0x14
Allocated by task 684:
kasan_kmalloc+0xe0/0x190
kmem_cache_alloc_trace+0x110/0x240
pci_alloc_dev+0x4c/0x110
pci_scan_single_device+0x100/0x218
pci_scan_slot+0x8c/0x2d8
pci_scan_child_bus_extend+0x90/0x628
pci_scan_child_bus+0x24/0x30
pci_scan_bridge_extend+0x3b8/0xb28
pci_scan_child_bus_extend+0x350/0x628
pci_rescan_bus+0x24/0x48
pcie_do_fatal_recovery+0x390/0x4b0
handle_error_source+0x124/0x158
aer_isr+0x5a0/0x800
process_one_work+0x598/0x1250
worker_thread+0x384/0xf08
kthread+0x2a4/0x320
ret_from_fork+0x10/0x18
Freed by task 685:
__kasan_slab_free+0x120/0x228
kasan_slab_free+0x10/0x18
kfree+0x88/0x218
pci_release_dev+0xb4/0xd8
device_release+0x6c/0x1c0
kobject_put+0x12c/0x400
put_device+0x24/0x30
pci_dev_put+0x24/0x30
handle_error_source+0x12c/0x158
aer_isr+0x5a0/0x800
process_one_work+0x598/0x1250
worker_thread+0x384/0xf08
kthread+0x2a4/0x320
ret_from_fork+0x10/0x18
The buggy address belongs to the object at fffffc3e2e402200
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 24 bytes inside of
4096-byte region [fffffc3e2e402200, fffffc3e2e403200)
The buggy address belongs to the page:
page:ffff7ff0f8b90000 count:1 mapcount:0 mapping:ffffdc365f016e00 index:0x0 compound_mapcount: 0
flags: 0x6ffffe0000008100(slab|head)
raw: 6ffffe0000008100 ffff7f70d83aae00 0000000300000003 ffffdc365f016e00
raw: 0000000000000000 0000000080070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
fffffc3e2e402100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
fffffc3e2e402180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>fffffc3e2e402200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
fffffc3e2e402280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
fffffc3e2e402300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
It is caused by the following race condition:
CPU0 CPU1
remove_store() aer_isr()
device_remove_file_self() handle_error_source()
pci_stop_and_remove_bus_device_locked pcie_do_fatal_recovery()
(blocked) pci_lock_rescan_remove() #CPU1 acquire the lock
pci_stop_and_remove_bus_device()
pci_unlock_rescan_remove() #CPU1 release the lock
pci_lock_rescan_remove() #CPU0 acquire the lock
pci_dev_put() #free pci_dev
pci_stop_and_remove_bus_device()
pci_stop_bus_device() #use-after-free
pci_unlock_rescan_remove()
An AER interrupt is triggered on CPU1. CPU1 starts to process it. A work
'aer_isr()' is scheduled on CPU1. It calling into
pcie_do_fatal_recovery(), and aquire lock 'pci_rescan_remove_lock'.
Before it removes the sysfs corresponding to the error pci device, a
sysfs remove operation is executed on CPU0. CPU0 use
device_remove_file_self() to remove the sysfs directory and wait for the
lock to be released. After CPU1 finish pci_stop_and_remove_bus_device(),
it release the lock and free the 'pci_dev' in pci_dev_put(). CPU0 acquire
the lock and access the 'pci_dev'. Then a use-after-free is triggered.
To fix this issue, we increase the reference count in remove_store()
before remove the device and decrease the reference count in the end.
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
---
drivers/pci/pci-sysfs.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 5d63df7c1820..2188e0c637fc 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -462,13 +462,17 @@ static struct device_attribute dev_attr_dev_rescan = __ATTR(rescan, 0200, NULL,
static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
+ struct pci_dev *pdev = to_pci_dev(dev);
unsigned long val;
if (kstrtoul(buf, 0, &val) < 0)
return -EINVAL;
+ pci_dev_get(pdev);
if (val && device_remove_file_self(dev, attr))
- pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
+ pci_stop_and_remove_bus_device_locked(pdev);
+ pci_dev_put(pdev);
+
return count;
}
static DEVICE_ATTR_IGNORE_LOCKDEP(remove, 0220, NULL,
--
2.20.1
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