misc: pci_endpoint_test: Prevent some integer overflows

"size + max" can have an arithmetic overflow when we're allocating:

  orig_src_addr = dma_alloc_coherent(dev, size + alignment, ...

Add a few checks to prevent that.

Fixes: 13107c6 ("misc: pci_endpoint_test: Add support to provide aligned buffer addresses")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>

drivers/misc/pci_endpoint_test.c

@@ -226,6 +226,9 @@ static bool pci_endpoint_test_copy(struct pci_endpoint_test *test, size_t size)
 	u32 src_crc32;
 	u32 dst_crc32;
 
+	if (size > SIZE_MAX - alignment)
+		goto err;
+
 	orig_src_addr = dma_alloc_coherent(dev, size + alignment,
 					   &orig_src_phys_addr, GFP_KERNEL);
 	if (!orig_src_addr) {
@@ -311,6 +314,9 @@ static bool pci_endpoint_test_write(struct pci_endpoint_test *test, size_t size)
 	size_t alignment = test->alignment;
 	u32 crc32;
 
+	if (size > SIZE_MAX - alignment)
+		goto err;
+
 	orig_addr = dma_alloc_coherent(dev, size + alignment, &orig_phys_addr,
 				       GFP_KERNEL);
 	if (!orig_addr) {
@@ -369,6 +375,9 @@ static bool pci_endpoint_test_read(struct pci_endpoint_test *test, size_t size)
 	size_t alignment = test->alignment;
 	u32 crc32;
 
+	if (size > SIZE_MAX - alignment)
+		goto err;
+
 	orig_addr = dma_alloc_coherent(dev, size + alignment, &orig_phys_addr,
 				       GFP_KERNEL);
 	if (!orig_addr) {