nfc: pn533: Wait for out_urb's completion in pn533_usb_send_frame()

Fix a use-after-free that occurs in hcd when in_urb sent from
pn533_usb_send_frame() is completed earlier than out_urb. Its callback
frees the skb data in pn533_send_async_complete() that is used as a
transfer buffer of out_urb. Wait before sending in_urb until the
callback of out_urb is called. To modify the callback of out_urb alone,
separate the complete function of out_urb and ack_urb.

Found by a modified version of syzkaller.

BUG: KASAN: use-after-free in dummy_timer
Call Trace:
 memcpy (mm/kasan/shadow.c:65)
 dummy_perform_transfer (drivers/usb/gadget/udc/dummy_hcd.c:1352)
 transfer (drivers/usb/gadget/udc/dummy_hcd.c:1453)
 dummy_timer (drivers/usb/gadget/udc/dummy_hcd.c:1972)
 arch_static_branch (arch/x86/include/asm/jump_label.h:27)
 static_key_false (include/linux/jump_label.h:207)
 timer_expire_exit (include/trace/events/timer.h:127)
 call_timer_fn (kernel/time/timer.c:1475)
 expire_timers (kernel/time/timer.c:1519)
 __run_timers (kernel/time/timer.c:1790)
 run_timer_softirq (kernel/time/timer.c:1803)

Fixes: c46ee386 ("NFC: pn533: add NXP pn533 nfc device driver")
Signed-off-by: Minsuk Kang <linuxlovemin@yonsei.ac.kr>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/nfc/pn533/usb.c

@@ -153,10 +153,17 @@ static int pn533_usb_send_ack(struct pn533 *dev, gfp_t flags)
 	return usb_submit_urb(phy->ack_urb, flags);
 }
 
+struct pn533_out_arg {
+	struct pn533_usb_phy *phy;
+	struct completion done;
+};
+
 static int pn533_usb_send_frame(struct pn533 *dev,
 				struct sk_buff *out)
 {
 	struct pn533_usb_phy *phy = dev->phy;
+	struct pn533_out_arg arg;
+	void *cntx;
 	int rc;
 
 	if (phy->priv == NULL)
@@ -168,10 +175,17 @@ static int pn533_usb_send_frame(struct pn533 *dev,
 	print_hex_dump_debug("PN533 TX: ", DUMP_PREFIX_NONE, 16, 1,
 			     out->data, out->len, false);
 
+	init_completion(&arg.done);
+	cntx = phy->out_urb->context;
+	phy->out_urb->context = &arg;
+
 	rc = usb_submit_urb(phy->out_urb, GFP_KERNEL);
 	if (rc)
 		return rc;
 
+	wait_for_completion(&arg.done);
+	phy->out_urb->context = cntx;
+
 	if (dev->protocol_type == PN533_PROTO_REQ_RESP) {
 		/* request for response for sent packet directly */
 		rc = pn533_submit_urb_for_response(phy, GFP_KERNEL);
@@ -408,7 +422,31 @@ static int pn533_acr122_poweron_rdr(struct pn533_usb_phy *phy)
 	return arg.rc;
 }
 
-static void pn533_send_complete(struct urb *urb)
+static void pn533_out_complete(struct urb *urb)
+{
+	struct pn533_out_arg *arg = urb->context;
+	struct pn533_usb_phy *phy = arg->phy;
+
+	switch (urb->status) {
+	case 0:
+		break; /* success */
+	case -ECONNRESET:
+	case -ENOENT:
+		dev_dbg(&phy->udev->dev,
+			"The urb has been stopped (status %d)\n",
+			urb->status);
+		break;
+	case -ESHUTDOWN:
+	default:
+		nfc_err(&phy->udev->dev,
+			"Urb failure (status %d)\n",
+			urb->status);
+	}
+
+	complete(&arg->done);
+}
+
+static void pn533_ack_complete(struct urb *urb)
 {
 	struct pn533_usb_phy *phy = urb->context;
 
@@ -496,10 +534,10 @@ static int pn533_usb_probe(struct usb_interface *interface,
 
 	usb_fill_bulk_urb(phy->out_urb, phy->udev,
 			  usb_sndbulkpipe(phy->udev, out_endpoint),
-			  NULL, 0, pn533_send_complete, phy);
+			  NULL, 0, pn533_out_complete, phy);
 	usb_fill_bulk_urb(phy->ack_urb, phy->udev,
 			  usb_sndbulkpipe(phy->udev, out_endpoint),
-			  NULL, 0, pn533_send_complete, phy);
+			  NULL, 0, pn533_ack_complete, phy);
 
 	switch (id->driver_info) {
 	case PN533_DEVICE_STD: