PCI: Check BAR index for validity

Many functions in PCI use accessor macros such as pci_resource_len(),
which take a BAR index. That index, however, is never checked for
validity, potentially resulting in undefined behavior by overflowing the
array pci_dev.resource in the macro pci_resource_n().

Since many users of those macros directly assign the accessed value to
an unsigned integer, the macros cannot be changed easily anymore to
return -EINVAL for invalid indexes. Consequently, the problem has to be
mitigated in higher layers.

Add pci_bar_index_valid(). Use it where appropriate.

Link: https://lore.kernel.org/r/[email protected]
Closes: https://lore.kernel.org/all/[email protected]/
Reported-by: Bingbu Cao <[email protected]>
Signed-off-by: Philipp Stanner <[email protected]>
[kwilczynski: correct if-statement condition the pci_bar_index_is_valid()
helper function uses, tidy up code comments]
Signed-off-by: Krzysztof Wilczyński <[email protected]>
[bhelgaas: fix typo]
Signed-off-by: Bjorn Helgaas <[email protected]>

Author: Philipp Stanner

drivers/pci/devres.c

@@ -577,7 +577,7 @@ static int pcim_add_mapping_to_legacy_table(struct pci_dev *pdev,
 {
 	void __iomem **legacy_iomap_table;
 
-	if (bar >= PCI_STD_NUM_BARS)
+	if (!pci_bar_index_is_valid(bar))
 		return -EINVAL;
 
 	legacy_iomap_table = (void __iomem **)pcim_iomap_table(pdev);
@@ -622,7 +622,7 @@ static void pcim_remove_bar_from_legacy_table(struct pci_dev *pdev, int bar)
 {
 	void __iomem **legacy_iomap_table;
 
-	if (bar >= PCI_STD_NUM_BARS)
+	if (!pci_bar_index_is_valid(bar))
 		return;
 
 	legacy_iomap_table = (void __iomem **)pcim_iomap_table(pdev);
@@ -655,6 +655,9 @@ void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen)
 	void __iomem *mapping;
 	struct pcim_addr_devres *res;
 
+	if (!pci_bar_index_is_valid(bar))
+		return NULL;
+
 	res = pcim_addr_devres_alloc(pdev);
 	if (!res)
 		return NULL;
@@ -722,6 +725,9 @@ void __iomem *pcim_iomap_region(struct pci_dev *pdev, int bar,
 	int ret;
 	struct pcim_addr_devres *res;
 
+	if (!pci_bar_index_is_valid(bar))
+		return IOMEM_ERR_PTR(-EINVAL);
+
 	res = pcim_addr_devres_alloc(pdev);
 	if (!res)
 		return IOMEM_ERR_PTR(-ENOMEM);
@@ -823,6 +829,9 @@ static int _pcim_request_region(struct pci_dev *pdev, int bar, const char *name,
 	int ret;
 	struct pcim_addr_devres *res;
 
+	if (!pci_bar_index_is_valid(bar))
+		return -EINVAL;
+
 	res = pcim_addr_devres_alloc(pdev);
 	if (!res)
 		return -ENOMEM;
@@ -991,6 +1000,9 @@ void __iomem *pcim_iomap_range(struct pci_dev *pdev, int bar,
 	void __iomem *mapping;
 	struct pcim_addr_devres *res;
 
+	if (!pci_bar_index_is_valid(bar))
+		return IOMEM_ERR_PTR(-EINVAL);
+
 	res = pcim_addr_devres_alloc(pdev);
 	if (!res)
 		return IOMEM_ERR_PTR(-ENOMEM);

drivers/pci/iomap.c

@@ -9,6 +9,8 @@
 
 #include <linux/export.h>
 
+#include "pci.h" /* for pci_bar_index_is_valid() */
+
 /**
  * pci_iomap_range - create a virtual mapping cookie for a PCI BAR
  * @dev: PCI device that owns the BAR
@@ -33,12 +35,19 @@ void __iomem *pci_iomap_range(struct pci_dev *dev,
 			      unsigned long offset,
 			      unsigned long maxlen)
 {
-	resource_size_t start = pci_resource_start(dev, bar);
-	resource_size_t len = pci_resource_len(dev, bar);
-	unsigned long flags = pci_resource_flags(dev, bar);
+	resource_size_t start, len;
+	unsigned long flags;
+
+	if (!pci_bar_index_is_valid(bar))
+		return NULL;
+
+	start = pci_resource_start(dev, bar);
+	len = pci_resource_len(dev, bar);
+	flags = pci_resource_flags(dev, bar);
 
 	if (len <= offset || !start)
 		return NULL;
+
 	len -= offset;
 	start += offset;
 	if (maxlen && len > maxlen)
@@ -77,16 +86,20 @@ void __iomem *pci_iomap_wc_range(struct pci_dev *dev,
 				 unsigned long offset,
 				 unsigned long maxlen)
 {
-	resource_size_t start = pci_resource_start(dev, bar);
-	resource_size_t len = pci_resource_len(dev, bar);
-	unsigned long flags = pci_resource_flags(dev, bar);
+	resource_size_t start, len;
+	unsigned long flags;
 
-
-	if (flags & IORESOURCE_IO)
+	if (!pci_bar_index_is_valid(bar))
 		return NULL;
 
+	start = pci_resource_start(dev, bar);
+	len = pci_resource_len(dev, bar);
+	flags = pci_resource_flags(dev, bar);
+
 	if (len <= offset || !start)
 		return NULL;
+	if (flags & IORESOURCE_IO)
+		return NULL;
 
 	len -= offset;
 	start += offset;

drivers/pci/pci.c

@@ -3921,6 +3921,9 @@ EXPORT_SYMBOL(pci_enable_atomic_ops_to_root);
  */
 void pci_release_region(struct pci_dev *pdev, int bar)
 {
+	if (!pci_bar_index_is_valid(bar))
+		return;
+
 	/*
 	 * This is done for backwards compatibility, because the old PCI devres
 	 * API had a mode in which the function became managed if it had been
@@ -3965,6 +3968,9 @@ EXPORT_SYMBOL(pci_release_region);
 static int __pci_request_region(struct pci_dev *pdev, int bar,
 				const char *name, int exclusive)
 {
+	if (!pci_bar_index_is_valid(bar))
+		return -EINVAL;
+
 	if (pci_is_managed(pdev)) {
 		if (exclusive == IORESOURCE_EXCLUSIVE)
 			return pcim_request_region_exclusive(pdev, bar, name);

drivers/pci/pci.h

@@ -167,6 +167,22 @@ static inline void pci_wakeup_event(struct pci_dev *dev)
 	pm_wakeup_event(&dev->dev, 100);
 }
 
+/**
+ * pci_bar_index_is_valid - Check whether a BAR index is within valid range
+ * @bar: BAR index
+ *
+ * Protects against overflowing &struct pci_dev.resource array.
+ *
+ * Return: true for valid index, false otherwise.
+ */
+static inline bool pci_bar_index_is_valid(int bar)
+{
+	if (bar >= 0 && bar < PCI_NUM_RESOURCES)
+		return true;
+
+	return false;
+}
+
 static inline bool pci_has_subordinate(struct pci_dev *pci_dev)
 {
 	return !!(pci_dev->subordinate);