[PATCH 5.14 046/151] PCI: hv: Fix sleep while in non-sleep context when removing child devices from the bus

Greg Kroah-Hartman
2021-10-11T14:03:38Z

From: Long Li <longli@microsoft.com>

[ Upstream commit 41608b64b10b80fe00dd253cd8326ec8ad85930f ]

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>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/1630365207-20616-1-git-send-email-longli@linuxonhyperv.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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);
--
2.33.0