linux-kernel - [PATCH 0/2] use-after-free issues in configfs

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Message-Id: <20221104131031.850850-1-s.hauer@pengutronix.de>
Date:   Fri,  4 Nov 2022 14:10:29 +0100
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     linux-usb@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        Sascha Hauer <s.hauer@...gutronix.de>
Subject: [PATCH 0/2] use-after-free issues in configfs

This series addresses a few problems with the users of the gether code.
The problem arises when a UDC is disconnected from a gadget created with
configfs doing a "echo '' > UDC". It seems the existing code is tested
up to the point where the gadget from configfs is up, tearing it down
still seems to make problems. I for myself am also not interested in tearing
it down, but I see use-after-free issues when doing a reboot -f.

The underlying problem is that the eth_dev returned by the gether code is used
for multiple bind/unbind cycles, but only initialized properly once.

The usb_gadget * is only valid between bind and unbind, so it is not a suitable
parent for the net_device whose lifetime spans multiple bind/unbind cycles.

I solved the issues for the f_ecm driver, similar problems exist in the other users
like f_eem or f_ncm as well. I can prepare patches for these once it's clear
that this is really the way to go.

Sascha Hauer (2):
  usb: gadget: u_ether: Do not make UDC parent of the net device
  usb: gadget: f_ecm: Always set current gadget in ecm_bind()

 drivers/usb/gadget/function/f_ecm.c   | 22 +++++++++-------------
 drivers/usb/gadget/function/u_ether.c |  4 ----
 2 files changed, 9 insertions(+), 17 deletions(-)

-- 
2.30.2