PCI: endpoint: Fix for concurrent memory allocation in OB address region

pci-epc-mem uses a bitmap to manage the Endpoint outbound (OB) address
region. This address region will be shared by multiple endpoint
functions (in the case of multi function endpoint) and it has to be
protected from concurrent access to avoid updating an inconsistent state.

Use a mutex to protect bitmap updates to prevent the memory
allocation API from returning incorrect addresses.
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: stable@vger.kernel.org # v4.14+

drivers/pci/endpoint/pci-epc-mem.c

@@ -79,6 +79,7 @@ int __pci_epc_mem_init(struct pci_epc *epc, phys_addr_t phys_base, size_t size,
 	mem->page_size = page_size;
 	mem->pages = pages;
 	mem->size = size;
+	mutex_init(&mem->lock);
 
 	epc->mem = mem;
 
@@ -122,7 +123,7 @@ void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
 				     phys_addr_t *phys_addr, size_t size)
 {
 	int pageno;
-	void __iomem *virt_addr;
+	void __iomem *virt_addr = NULL;
 	struct pci_epc_mem *mem = epc->mem;
 	unsigned int page_shift = ilog2(mem->page_size);
 	int order;
@@ -130,15 +131,18 @@ void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
 	size = ALIGN(size, mem->page_size);
 	order = pci_epc_mem_get_order(mem, size);
 
+	mutex_lock(&mem->lock);
 	pageno = bitmap_find_free_region(mem->bitmap, mem->pages, order);
 	if (pageno < 0)
-		return NULL;
+		goto ret;
 
 	*phys_addr = mem->phys_base + ((phys_addr_t)pageno << page_shift);
 	virt_addr = ioremap(*phys_addr, size);
 	if (!virt_addr)
 		bitmap_release_region(mem->bitmap, pageno, order);
 
+ret:
+	mutex_unlock(&mem->lock);
 	return virt_addr;
 }
 EXPORT_SYMBOL_GPL(pci_epc_mem_alloc_addr);
@@ -164,7 +168,9 @@ void pci_epc_mem_free_addr(struct pci_epc *epc, phys_addr_t phys_addr,
 	pageno = (phys_addr - mem->phys_base) >> page_shift;
 	size = ALIGN(size, mem->page_size);
 	order = pci_epc_mem_get_order(mem, size);
+	mutex_lock(&mem->lock);
 	bitmap_release_region(mem->bitmap, pageno, order);
+	mutex_unlock(&mem->lock);
 }
 EXPORT_SYMBOL_GPL(pci_epc_mem_free_addr);
 

include/linux/pci-epc.h

@@ -71,6 +71,7 @@ struct pci_epc_ops {
  * @bitmap: bitmap to manage the PCI address space
  * @pages: number of bits representing the address region
  * @page_size: size of each page
+ * @lock: mutex to protect bitmap
  */
 struct pci_epc_mem {
 	phys_addr_t	phys_base;
@@ -78,6 +79,8 @@ struct pci_epc_mem {
 	unsigned long	*bitmap;
 	size_t		page_size;
 	int		pages;
+	/* mutex to protect against concurrent access for memory allocation*/
+	struct mutex	lock;
 };
 
 /**