tee: amdtee: out of bounds read in find_session()

The "index" is a user provided value from 0-USHRT_MAX.  If it's over
TEE_NUM_SESSIONS (31) then it results in an out of bounds read when we
call test_bit(index, sess->sess_mask).

Fixes: 757cc3e9 ("tee: add AMD-TEE driver")
Acked-by: Rijo Thomas <Rijo-john.Thomas@amd.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/amdtee/core.c

@@ -139,6 +139,9 @@ static struct amdtee_session *find_session(struct amdtee_context_data *ctxdata,
 	u32 index = get_session_index(session);
 	struct amdtee_session *sess;
 
+	if (index >= TEE_NUM_SESSIONS)
+		return NULL;
+
 	list_for_each_entry(sess, &ctxdata->sess_list, list_node)
 		if (ta_handle == sess->ta_handle &&
 		    test_bit(index, sess->sess_mask))