linux-kernel - [PATCH v2 0/6] USB: gadget: f

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Date:   Mon, 28 Oct 2019 11:42:22 +0000
From:   John Keeping <john@...anate.com>
To:     linux-usb@...r.kernel.org
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, John Keeping <john@...anate.com>
Subject: [PATCH v2 0/6] USB: gadget: f_hid: fix lifetime issues

File descriptors referencing the /dev/hidgN device created by the HID
gadget can outlive the underlying gadget function, which creates easy to
trigger use-after-frees in the kernel.

A simple reproduction for this using the libusbgx example programs is:

	$ gadget-hid
	$ exec 3<> /dev/hidg0
	$ gadget-vid-pid-remove
	$ exec 3<&-

Closing the file descriptor on the last line triggers a use-after-free
which can be seen immediately with slub_debug=P.

This series fixes this by making the struct cdev associated with the
module rather than dynamically allocated for the gadget and changing
struct f_hidg to be refcounted instead of tied to the gadget lifetime.

v2:
- Fix compiling as a module

John Keeping (6):
  USB: gadget: f_hid: move chardev setup to module init
  USB: gadget: f_hid: switch to IDR for tracking minors
  USB: gadget: f_hid: find f_hidg by IDR lookup on open
  USB: gadget: f_hid: decouple cdev from f_hidg lifetime
  USB: gadget: f_hid: refcount f_hidg structure
  USB: gadget: f_hid: return ENODEV from read/write after deletion

 drivers/usb/gadget/function/f_hid.c | 150 +++++++++++++++++++---------
 drivers/usb/gadget/function/u_hid.h |   3 -
 2 files changed, 103 insertions(+), 50 deletions(-)

-- 
2.23.0