[PATCH] PCI: hv: Fix a bug on removing child devices on the bus

From: longli
Date: Tue Aug 24 2021 - 03:20:32 EST

From: Long Li <longli@xxxxxxxxxxxxx>

In hv_pci_bus_exit, the code is holding a spinlock while calling
pci_destroy_slot(), which takes a mutex.

This is not safe for spinlock. Fix this by moving the children to be
deleted to a list on the stack, and removing them after spinlock is

Fixes: 94d22763207a ("PCI: hv: Fix a race condition when removing the device")

Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Cc: Rob Herring <robh@xxxxxxxxxx>
Cc: "Krzysztof Wilczyński" <kw@xxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
drivers/pci/controller/pci-hyperv.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index a53bd8728d0d..d4f3cce18957 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -3220,6 +3220,7 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
struct hv_pci_dev *hpdev, *tmp;
unsigned long flags;
int ret;
+ struct list_head removed;

* After the host sends the RESCIND_CHANNEL message, it doesn't
@@ -3229,9 +3230,18 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
return 0;

if (!keep_devs) {
- /* Delete any children which might still exist. */
+ INIT_LIST_HEAD(&removed);
+ /* Move all present children to the list on stack */
spin_lock_irqsave(&hbus->device_list_lock, flags);
- list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry) {
+ list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry)
+ list_move_tail(&hpdev->list_entry, &removed);
+ spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+ /* Remove all children in the list */
+ while (!list_empty(&removed)) {
+ hpdev = list_first_entry(&removed, struct hv_pci_dev,
+ list_entry);
if (hpdev->pci_slot)
@@ -3239,7 +3249,6 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
- spin_unlock_irqrestore(&hbus->device_list_lock, flags);

ret = hv_send_resources_released(hdev);