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PCI: hv: Fix sleep while in non-sleep context when removing child devices from the bus

PATCH Applied [email protected] 2 participants 3 messages Aug 30, 2021 – Sep 24, 2021

Subsystems (4)
PCI PCI native host bridge and endpoint drivers Hyper-V/Azure core and drivers Microsoft MANA RDMA driver
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#0 lore raw

PATCH v2 1/1 PCI: hv: Fix sleep while in non-sleep context when removing child devices from the bus

From: Long Li <[email protected]>

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 released.

Fixes 94d22763207a ("PCI: hv: Fix a race condition when removing the device")
Cc "K. Y. Srinivasan" <[email protected]>
Cc Haiyang Zhang <[email protected]>
Cc Stephen Hemminger <[email protected]>
Cc Wei Liu <[email protected]>
Cc Dexuan Cui <[email protected]>
Cc Lorenzo Pieralisi <[email protected]>
Cc Rob Herring <[email protected]>
Cc "Krzysztof Wilczyński" <[email protected]>
Cc Bjorn Helgaas <[email protected]>
Cc Michael Kelley <[email protected]>
Reported-by Dan Carpenter <[email protected]>
Link https://lore.kernel.org/linux-hyperv/20210823152130.GA21501@kili/ open here
Signed-off-by Long Li <[email protected]>

---
Changes in v2:
Made patch title more specific on what the patch does. Added link to the original bug report.
Changed to list_for_each_entry_safe for iterating the removed list.

 drivers/pci/controller/pci-hyperv.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)
drivers/pci/controller/pci-hyperv.c +10 -3
index a53bd8728d0d..fc1a29acadbb 100644
@@ -3229,9 +3229,17 @@ 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. */
+		struct list_head removed;
+
+		/* Move all present children to the list on stack */
+		INIT_LIST_HEAD(&removed);
 		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 */
+		list_for_each_entry_safe(hpdev, tmp, &removed, list_entry) {
 			list_del(&hpdev->list_entry);
 			if (hpdev->pci_slot)
 				pci_destroy_slot(hpdev->pci_slot);

@@ -3239,7 +3247,6 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
 			put_pcichild(hpdev);
 			put_pcichild(hpdev);
 		}
-		spin_unlock_irqrestore(&hbus->device_list_lock, flags);
 	}
 
 	ret = hv_send_resources_released(hdev);
Signature · 1 line
2.25.1
maintainer Reviewed-by on v2 1/1
#1 lore raw
Quoted 11 lines · On Mon, Aug 30, 2021 at 04:13:27PM -0700, [email protected] wrote:

From: Long Li <[email protected]>

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 released.

Fixes 94d22763207a ("PCI: hv: Fix a race condition when removing the device")
Quoted 13 lines
Cc "K. Y. Srinivasan" <[email protected]>
Cc Haiyang Zhang <[email protected]>
Cc Stephen Hemminger <[email protected]>
Cc Wei Liu <[email protected]>
Cc Dexuan Cui <[email protected]>
Cc Lorenzo Pieralisi <[email protected]>
Cc Rob Herring <[email protected]>
Cc "Krzysztof Wilczyński" <[email protected]>
Cc Bjorn Helgaas <[email protected]>
Cc Michael Kelley <[email protected]>
Reported-by Dan Carpenter <[email protected]>
Link https://lore.kernel.org/linux-hyperv/20210823152130.GA21501@kili/ open here
Signed-off-by Long Li <[email protected]>
Reviewed-by Wei Liu <[email protected]>
maintainer Applied
#2 lore raw
Quoted 26 lines · Wei Liu
Quoted 11 lines · On Mon, Aug 30, 2021 at 04:13:27PM -0700, [email protected] wrote:

From: Long Li <[email protected]>

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 released.

Fixes 94d22763207a ("PCI: hv: Fix a race condition when removing the device")
Quoted 13 lines
Cc "K. Y. Srinivasan" <[email protected]>
Cc Haiyang Zhang <[email protected]>
Cc Stephen Hemminger <[email protected]>
Cc Wei Liu <[email protected]>
Cc Dexuan Cui <[email protected]>
Cc Lorenzo Pieralisi <[email protected]>
Cc Rob Herring <[email protected]>
Cc "Krzysztof Wilczyński" <[email protected]>
Cc Bjorn Helgaas <[email protected]>
Cc Michael Kelley <[email protected]>
Reported-by Dan Carpenter <[email protected]>
Link https://lore.kernel.org/linux-hyperv/20210823152130.GA21501@kili/ open here
Signed-off-by Long Li <[email protected]>
Quoted 1 line
Reviewed-by Wei Liu <[email protected]>

Applied to hyperv-fixes.