[PATCH v3] staging: emxx_udc: Add checks for dma_alloc_coherent()

[Yuan Can <yuancan@huawei.com>]

As the dma_alloc_coherent may return NULL, the return value needs to be
checked to avoid NULL poineter dereference.

Fixes: 33aa8d45a4fe ("staging: emxx_udc: Add Emma Mobile USB Gadget driver")
Signed-off-by: Yuan Can <yuancan@huawei.com>
---
changes in v2:
- do the null pointer check right before the memcpy().
changes in v3:
- do the null pointer check right after the dma_alloc_coherent().

 drivers/staging/emxx_udc/emxx_udc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/emxx_udc/emxx_udc.c b/drivers/staging/emxx_udc/emxx_udc.c
index b4e19174bef2..f9765841c4aa 100644
--- a/drivers/staging/emxx_udc/emxx_udc.c
+++ b/drivers/staging/emxx_udc/emxx_udc.c
@@ -2587,10 +2587,15 @@ static int nbu2ss_ep_queue(struct usb_ep *_ep,
 		req->unaligned = false;
 
 	if (req->unaligned) {
-		if (!ep->virt_buf)
+		if (!ep->virt_buf) {
 			ep->virt_buf = dma_alloc_coherent(udc->dev, PAGE_SIZE,
 							  &ep->phys_buf,
 							  GFP_ATOMIC | GFP_DMA);
+			if (!ep->virt_buf) {
+				spin_unlock_irqrestore(&udc->lock, flags);
+				return -ENOMEM;
+			}
+		}
 		if (ep->epnum > 0)  {
 			if (ep->direct == USB_DIR_IN)
 				memcpy(ep->virt_buf, req->req.buf,
-- 
2.17.1