drivers:misc: ti-st: fail-safe on wrong pkt type

Texas Instrument's shared transport driver interpret incoming data from the
UART based on the various protocol drivers registered to the driver such as
btwilink driver or FM or GPS driver which provide logical channel IDs.

In case of bad-behavior from chip such as HCI Event response for a GPS command
or a HCI Event (h/w error event) for a FM response & In case of bad-behavior
from UART driver such as dropping data bytes a fail-safe is required to avoid
kernel panic.

Signed-off-by: Pavan Savoy <pavan_savoy@ti.com>
Signed-off-by: Vijay Badawadagi <bvijay@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/misc/ti-st/st_core.c

@@ -338,6 +338,12 @@ void st_int_recv(void *disc_data,
 			/* Unknow packet? */
 		default:
 			type = *ptr;
+			if (st_gdata->list[type] == NULL) {
+				pr_err("chip/interface misbehavior dropping"
+					" frame starting with 0x%02x", type);
+				goto done;
+
+			}
 			st_gdata->rx_skb = alloc_skb(
 					st_gdata->list[type]->max_frame_size,
 					GFP_ATOMIC);
@@ -354,6 +360,7 @@ void st_int_recv(void *disc_data,
 		ptr++;
 		count--;
 	}
+done:
 	spin_unlock_irqrestore(&st_gdata->lock, flags);
 	pr_debug("done %s", __func__);
 	return;