[PATCH v3] usb: gadget: aspeed_udc: Add check for dma_alloc_coherent

[Jiasheng Jiang]

Add the check for the return value of dma_alloc_coherent in order to
avoid NULL pointer dereference.

This flaw was found using an experimental static analysis tool we are
developing, APP-Miner, which has not been disclosed.

The allyesconfig build using GCC 9.3.0 shows no new warning. As we
don't have a UDC device to test with, no runtime testing was able to
be performed.

Signed-off-by: Jiasheng Jiang <jiasheng@xxxxxxxxxxx>
---
Changelog:

v2 -> v3:

1. Add information of finding tool and tests to commit message.

v1 -> v2:

1. Add "goto err;" when allocation fails.
---
 drivers/usb/gadget/udc/aspeed_udc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/gadget/udc/aspeed_udc.c b/drivers/usb/gadget/udc/aspeed_udc.c
index 01968e2167f9..7dc2457c7460 100644
--- a/drivers/usb/gadget/udc/aspeed_udc.c
+++ b/drivers/usb/gadget/udc/aspeed_udc.c
@@ -1516,6 +1516,10 @@ static int ast_udc_probe(struct platform_device *pdev)
 					  AST_UDC_EP_DMA_SIZE *
 					  AST_UDC_NUM_ENDPOINTS,
 					  &udc->ep0_buf_dma, GFP_KERNEL);
+	if (!udc->ep0_buf) {
+		rc = -ENOMEM;
+		goto err;
+	}
 
 	udc->gadget.speed = USB_SPEED_UNKNOWN;
 	udc->gadget.max_speed = USB_SPEED_HIGH;
-- 
2.25.1