linux-kernel - [PATCH] usb: roles: fix a potential use after free

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Message-Id: <20191124142236.25671-1-wenyang@linux.alibaba.com>
Date:   Sun, 24 Nov 2019 22:22:36 +0800
From:   Wen Yang <wenyang@...ux.alibaba.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Wen Yang <wenyang@...ux.alibaba.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] usb: roles: fix a potential use after free

Free the sw structure only after we are done using it.
This patch just moves the put_device() down a bit to avoid the
use after free.

Fixes: 5c54fcac9a9d ("usb: roles: Take care of driver module reference counting")
Signed-off-by: Wen Yang <wenyang@...ux.alibaba.com>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: Hans de Goede <hdegoede@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Chunfeng Yun <chunfeng.yun@...iatek.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-usb@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/usb/roles/class.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
index 8273126..63a00ff 100644
--- a/drivers/usb/roles/class.c
+++ b/drivers/usb/roles/class.c
@@ -169,8 +169,8 @@ struct usb_role_switch *fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
 void usb_role_switch_put(struct usb_role_switch *sw)
 {
 	if (!IS_ERR_OR_NULL(sw)) {
-		put_device(&sw->dev);
 		module_put(sw->dev.parent->driver->owner);
+		put_device(&sw->dev);
 	}
 }
 EXPORT_SYMBOL_GPL(usb_role_switch_put);
-- 
1.8.3.1