[PATCH 5.6 001/118] thunderbolt: Check return value of tb_sw_read() in usb4_switch_op()

[Greg Kroah-Hartman]

From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>

commit c3bf9930921b33edb31909006607e478751a6f5e upstream.

The function misses checking return value of tb_sw_read() before it
accesses the value that was read. Fix this by checking the return value
first.

Fixes: b04079837b20 ("thunderbolt: Add initial support for USB4")
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Reviewed-by: Yehezkel Bernat <yehezkelshb@xxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/thunderbolt/usb4.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/thunderbolt/usb4.c
+++ b/drivers/thunderbolt/usb4.c
@@ -182,6 +182,9 @@ static int usb4_switch_op(struct tb_swit
 		return ret;
 
 	ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, ROUTER_CS_26, 1);
+	if (ret)
+		return ret;
+
 	if (val & ROUTER_CS_26_ONS)
 		return -EOPNOTSUPP;