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Commit 248e65f3 authored by Lukas Wunner's avatar Lukas Wunner Committed by Greg Kroah-Hartman
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PCI: pciehp: Avoid returning prematurely from sysfs requests 

commit 157c1062fcd86ade3c674503705033051fd3d401 upstream.

A sysfs request to enable or disable a PCIe hotplug slot should not
return before it has been carried out.  That is sought to be achieved by
waiting until the controller's "pending_events" have been cleared.

However the IRQ thread pciehp_ist() clears the "pending_events" before
it acts on them.  If pciehp_sysfs_enable_slot() / _disable_slot() happen
to check the "pending_events" after they have been cleared but while
pciehp_ist() is still running, the functions may return prematurely
with an incorrect return value.

Fix by introducing an "ist_running" flag which must be false before a sysfs
request is allowed to return.

Fixes: 32a8cef2 ("PCI: pciehp: Enable/disable exclusively from IRQ thread")
Link: https://lore.kernel.org/linux-pci/1562226638-54134-1-git-send-email-wangxiongfeng2@huawei.com
Link: https://lore.kernel.org/r/4174210466e27eb7e2243dd1d801d5f75baaffd8.1565345211.git.lukas@wunner.de


Reported-and-tested-by: default avatarXiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: default avatarLukas Wunner <lukas@wunner.de>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 253c77b5

drivers/pci/hotplug/pciehp.h

+2 −0
Original line number Diff line number Diff line
@@ -106,6 +106,7 @@ struct slot { 
 *	that has not yet been cleared by the user

 * @pending_events: used by the IRQ handler to save events retrieved from the

 *	Slot Status register for later consumption by the IRQ thread

 * @ist_running: flag to keep user request waiting while IRQ thread is running

 * @request_result: result of last user request submitted to the IRQ thread

 * @requester: wait queue to wake up on completion of user request,

 *	used for synchronous slot enable/disable request via sysfs
@@ -125,6 +126,7 @@ struct controller { 
	unsigned int notification_enabled:1;

	unsigned int power_fault_detected;

	atomic_t pending_events;

	unsigned int ist_running;

	int request_result;

	wait_queue_head_t requester;

};

drivers/pci/hotplug/pciehp_ctrl.c

+4 −2
Original line number Diff line number Diff line
@@ -383,7 +383,8 @@ int pciehp_sysfs_enable_slot(struct slot *p_slot) 
		ctrl->request_result = -ENODEV;

		pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);

		wait_event(ctrl->requester,

			   !atomic_read(&ctrl->pending_events));

			   !atomic_read(&ctrl->pending_events) &&

			   !ctrl->ist_running);

		return ctrl->request_result;

	case POWERON_STATE:

		ctrl_info(ctrl, "Slot(%s): Already in powering on state\n",
@@ -416,7 +417,8 @@ int pciehp_sysfs_disable_slot(struct slot *p_slot) 
		mutex_unlock(&p_slot->lock);

		pciehp_request(ctrl, DISABLE_SLOT);

		wait_event(ctrl->requester,

			   !atomic_read(&ctrl->pending_events));

			   !atomic_read(&ctrl->pending_events) &&

			   !ctrl->ist_running);

		return ctrl->request_result;

	case POWEROFF_STATE:

		ctrl_info(ctrl, "Slot(%s): Already in powering off state\n",

drivers/pci/hotplug/pciehp_hpc.c

+2 −0
Original line number Diff line number Diff line
@@ -620,6 +620,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id) 
	irqreturn_t ret;

	u32 events;



	ctrl->ist_running = true;

	pci_config_pm_runtime_get(pdev);



	/* rerun pciehp_isr() if the port was inaccessible on interrupt */
@@ -666,6 +667,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id) 
	up_read(&ctrl->reset_lock);



	pci_config_pm_runtime_put(pdev);

	ctrl->ist_running = false;

	wake_up(&ctrl->requester);

	return IRQ_HANDLED;

}