[Patch v2] PCI: hv: Fix sleep while in non-sleep context when removing child devices from the bus

* [Patch v2] PCI: hv: Fix sleep while in non-sleep context when removing child devices from the bus
@ 2021-08-30 23:13 longli
  2021-08-31 13:16 ` Wei Liu
  0 siblings, 1 reply; 3+ messages in thread
From: longli @ 2021-08-30 23:13 UTC (permalink / raw)
  To: linux-pci, linux-kernel, linux-hyperv
  Cc: Long Li, K. Y. Srinivasan, Haiyang Zhang, Stephen Hemminger,
	Wei Liu, Dexuan Cui, Lorenzo Pieralisi, Rob Herring,
	Krzysztof Wilczyński, Bjorn Helgaas, Michael Kelley

From: Long Li <longli@microsoft.com>

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" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Rob Herring <robh@kernel.org>
Cc: "Krzysztof Wilczyński" <kw@linux.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Michael Kelley <mikelley@microsoft.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/linux-hyperv/20210823152130.GA21501@kili/
Signed-off-by: Long Li <longli@microsoft.com>
---
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(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index a53bd8728d0d..fc1a29acadbb 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -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);
-- 
2.25.1


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