2021-08-30 23:15:39

by Long Li

Subject: [Patch v2] 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/
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(-)

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

2021-08-31 13:18:44

by Wei Liu

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

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")
>
> 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/
> Signed-off-by: Long Li <[email protected]>

Reviewed-by: Wei Liu <[email protected]>

2021-09-24 11:12:29

by Wei Liu

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

On Tue, Aug 31, 2021 at 01:16:07PM +0000, Wei Liu wrote:
> 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")
> >
> > 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/
> > Signed-off-by: Long Li <[email protected]>
>
> Reviewed-by: Wei Liu <[email protected]>

Applied to hyperv-fixes.