From: Mika Westerberg <mika.westerberg@linux.intel.com>
Date: Thu, 9 Apr 2020 10:18:10 +0300
Subject: thunderbolt: Check return value of tb_sw_read() in usb4_switch_op()
Git-commit: c3bf9930921b33edb31909006607e478751a6f5e
Patch-mainline: v5.7-rc5
References: jsc#SLE-14130

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@linux.intel.com>
Reviewed-by: Yehezkel Bernat <yehezkelshb@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
 drivers/thunderbolt/usb4.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
index 3d084cec136f..50c7534ba31e 100644
--- a/drivers/thunderbolt/usb4.c
+++ b/drivers/thunderbolt/usb4.c
@@ -182,6 +182,9 @@ static int usb4_switch_op(struct tb_switch *sw, u16 opcode, u8 *status)
 		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;