HID: wacom: use GFP_ATOMIC in wacom_wac_queue_flush()

commit 55f1ad5 upstream.

wacom_wac_queue_flush() is called via the .raw_event callback
(wacom_raw_event → wacom_wac_pen_serial_enforce → wacom_wac_queue_flush).
For USB HID devices, this callback is invoked from hid_irq_in(), which
is a URB completion handler running in atomic context. Using GFP_KERNEL
in this path can sleep, leading to a "scheduling while atomic" bug.

Use GFP_ATOMIC instead. The existing code already handles allocation
failure by skipping the fifo entry and continuing.

Reported-by: Sashiko-bot <sashiko-bot@kernel.org>
Fixes: 5e013ad ("HID: wacom: Remove static WACOM_PKGLEN_MAX limit")
Cc: stable@vger.kernel.org
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jinmo Yang <jinmo44.yang@gmail.com>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: omnij

drivers/hid/wacom_sys.c

@@ -76,7 +76,7 @@ static void wacom_wac_queue_flush(struct hid_device *hdev,
 		unsigned int count;
 		int err;
 
-		buf = kzalloc(size, GFP_KERNEL);
+		buf = kzalloc(size, GFP_ATOMIC);
 		if (!buf) {
 			kfifo_skip(fifo);
 			continue;