linux-kernel - [PATCH] usb: typec: Fix double free in typec_altmode_put

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Date: Tue,  2 Jan 2024 20:29:48 +0100
From: "Christian A. Ehrhardt" <lk@...e.de>
To: linux-kernel@...r.kernel.org
Cc: "Christian A. Ehrhardt" <lk@...e.de>,
	Chris Bainbridge <chris.bainbridge@...il.com>,
	RD Babiera <rdbabiera@...gle.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH] usb: typec: Fix double free in typec_altmode_put_partner

The altmode device nodes of a port partner and of cable
plugs hold a reference to the altmode of a port. The port's
altmode contains various back pointers but these do not
contribute to the reference count.

Thus, free the port's altmode device instead of doing a
double free on ourself.

Reported-By: Chris Bainbridge <chris.bainbridge@...il.com>
Fixes: b17b7fe6dd5c (usb: typec: class: fix typec_altmode_put_partner to put plugs)
Cc: RD Babiera <rdbabiera@...gle.com>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: stable@...r.kernel.org
Signed-off-by: Christian A. Ehrhardt <lk@...e.de>
---
 drivers/usb/typec/class.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index 16a670828dde..2da19feacd91 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -263,11 +263,13 @@ static void typec_altmode_put_partner(struct altmode *altmode)
 {
 	struct altmode *partner = altmode->partner;
 	struct typec_altmode *adev;
+	struct typec_altmode *partner_adev;
 
 	if (!partner)
 		return;
 
 	adev = &altmode->adev;
+	partner_adev = &partner->adev;
 
 	if (is_typec_plug(adev->dev.parent)) {
 		struct typec_plug *plug = to_typec_plug(adev->dev.parent);
@@ -276,7 +278,7 @@ static void typec_altmode_put_partner(struct altmode *altmode)
 	} else {
 		partner->partner = NULL;
 	}
-	put_device(&adev->dev);
+	put_device(&partner_adev->dev);
 }
 
 /**
-- 
2.40.1