PCI: Lock upstream bridge for pci_reset_function()

Fix a long-standing locking gap for missing pci_cfg_access_lock() while
manipulating bridge reset registers and configuration during
pci_reset_bus_function().

If there is an upstream bridge, lock it before locking the device itself.
pci_dev_lock() calls pci_cfg_access_lock(), which blocks the writing of PCI
config space by user space.

Add lockdep assertion via pci_dev->cfg_access_lock to verify
pci_dev->block_cfg_access is set.

Co-developed-by: Dan Williams <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Dan Williams <[email protected]>
Signed-off-by: Dave Jiang <[email protected]>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <[email protected]>

Author: davejiang

drivers/pci/access.c

@@ -275,6 +275,8 @@ void pci_cfg_access_lock(struct pci_dev *dev)
 {
 	might_sleep();
 
+	lock_map_acquire(&dev->cfg_access_lock);
+
 	raw_spin_lock_irq(&pci_lock);
 	if (dev->block_cfg_access)
 		pci_wait_cfg(dev);
@@ -329,6 +331,8 @@ void pci_cfg_access_unlock(struct pci_dev *dev)
 	raw_spin_unlock_irqrestore(&pci_lock, flags);
 
 	wake_up_all(&pci_cfg_wait);
+
+	lock_map_release(&dev->cfg_access_lock);
 }
 EXPORT_SYMBOL_GPL(pci_cfg_access_unlock);
 

drivers/pci/pci.c

@@ -4879,6 +4879,7 @@ void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
  */
 int pci_bridge_secondary_bus_reset(struct pci_dev *dev)
 {
+	lock_map_assert_held(&dev->cfg_access_lock);
 	pcibios_reset_secondary_bus(dev);
 
 	return pci_bridge_wait_for_secondary_bus(dev, "bus reset");
@@ -5245,11 +5246,20 @@ void pci_init_reset_methods(struct pci_dev *dev)
  */
 int pci_reset_function(struct pci_dev *dev)
 {
+	struct pci_dev *bridge;
 	int rc;
 
 	if (!pci_reset_supported(dev))
 		return -ENOTTY;
 
+	/*
+	 * If there's no upstream bridge, no locking is needed since there is
+	 * no upstream bridge configuration to hold consistent.
+	 */
+	bridge = pci_upstream_bridge(dev);
+	if (bridge)
+		pci_dev_lock(bridge);
+
 	pci_dev_lock(dev);
 	pci_dev_save_and_disable(dev);
 
@@ -5258,6 +5268,9 @@ int pci_reset_function(struct pci_dev *dev)
 	pci_dev_restore(dev);
 	pci_dev_unlock(dev);
 
+	if (bridge)
+		pci_dev_unlock(bridge);
+
 	return rc;
 }
 EXPORT_SYMBOL_GPL(pci_reset_function);

drivers/pci/probe.c

@@ -2543,6 +2543,9 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 	dev->dev.dma_mask = &dev->dma_mask;
 	dev->dev.dma_parms = &dev->dma_parms;
 	dev->dev.coherent_dma_mask = 0xffffffffull;
+	lockdep_register_key(&dev->cfg_access_key);
+	lockdep_init_map(&dev->cfg_access_lock, dev_name(&dev->dev),
+			 &dev->cfg_access_key, 0);
 
 	dma_set_max_seg_size(&dev->dev, 65536);
 	dma_set_seg_boundary(&dev->dev, 0xffffffff);

include/linux/lockdep.h

@@ -297,6 +297,9 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 		.wait_type_inner = _wait_type,		\
 		.lock_type = LD_LOCK_WAIT_OVERRIDE, }
 
+#define lock_map_assert_held(l)		\
+	lockdep_assert(lock_is_held(l) != LOCK_STATE_NOT_HELD)
+
 #else /* !CONFIG_LOCKDEP */
 
 static inline void lockdep_init_task(struct task_struct *task)
@@ -388,6 +391,8 @@ extern int lockdep_is_held(const void *);
 #define DEFINE_WAIT_OVERRIDE_MAP(_name, _wait_type)	\
 	struct lockdep_map __maybe_unused _name = {}
 
+#define lock_map_assert_held(l)			do { (void)(l); } while (0)
+
 #endif /* !LOCKDEP */
 
 #ifdef CONFIG_PROVE_LOCKING

include/linux/pci.h

@@ -413,6 +413,8 @@ struct pci_dev {
 	struct resource driver_exclusive_resource;	 /* driver exclusive resource ranges */
 
 	bool		match_driver;		/* Skip attaching driver */
+	struct lock_class_key cfg_access_key;
+	struct lockdep_map cfg_access_lock;
 
 	unsigned int	transparent:1;		/* Subtractive decode bridge */
 	unsigned int	io_window:1;		/* Bridge has I/O window */