From 248e65f3220e66fb70c25192d693b5499614dda4 Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Fri, 9 Aug 2019 12:28:43 +0200 Subject: [PATCH] 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: 32a8cef274fe ("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: Xiongfeng Wang Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Greg Kroah-Hartman --- drivers/pci/hotplug/pciehp.h | 2 ++ drivers/pci/hotplug/pciehp_ctrl.c | 6 ++++-- drivers/pci/hotplug/pciehp_hpc.c | 2 ++ 3 files changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h index 811cf83f956d..ef6071807072 100644 --- a/drivers/pci/hotplug/pciehp.h +++ b/drivers/pci/hotplug/pciehp.h @@ -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; }; diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index 9c397fa8704c..c71964e29b01 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -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", diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index a938abdb41ce..c3e3f5358b3b 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -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; } -- GitLab