HID: wacom: handle kzalloc() allocation failure in wacom_wac_queue_flush()

During wacom_wac_queue_flush() the code calls
kzalloc() to allocate a zero initialised buffer
which it uses as a storage buffer to get data
from the fifo via kfifo_out(). However it does not
check kzalloc() for allocation failure which returns
NULL and could potentially lead to a NULL deref.

Fix this by checking for kzalloc() failure and skipping
the current entry if allocation failure occurs.

Fixes: 5e013ad ("HID: wacom: Remove static WACOM_PKGLEN_MAX limit")
Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

Author: qasim-ijaz

drivers/hid/wacom_sys.c

@@ -70,10 +70,16 @@ static void wacom_wac_queue_flush(struct hid_device *hdev,
 {
 	while (!kfifo_is_empty(fifo)) {
 		int size = kfifo_peek_len(fifo);
-		u8 *buf = kzalloc(size, GFP_KERNEL);
+		u8 *buf;
 		unsigned int count;
 		int err;
 
+		buf = kzalloc(size, GFP_KERNEL);
+		if (!buf) {
+			kfifo_skip(fifo);
+			continue;
+		}
+
 		count = kfifo_out(fifo, buf, size);
 		if (count != size) {
 			// Hard to say what is the "right" action in this