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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Mon, 9 Mar 2020 17:51:19 +0100
Message-ID: <CAAeHK+wTbBC2Dm6GVXVqKTsn9gKg1_EZ5MggmLBMaA6wA-wq4w@mail.gmail.com>
Subject: Re: [PATCH v6 0/1] usb: gadget: add raw-gadget interface
To:     Felipe Balbi <balbi@kernel.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        USB list <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, Feb 24, 2020 at 5:17 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> On Mon, Feb 24, 2020 at 5:13 PM Andrey Konovalov <andreyknvl@google.com> wrote:
> >
> > This patchset (currently a single patch) adds a new userspace interface
> > for the USB Gadget subsystem called USB Raw Gadget. This is what is
> > currently being used to enable coverage-guided USB fuzzing with syzkaller:
> >
> > https://github.com/google/syzkaller/blob/master/docs/linux/external_fuzzing_usb.md
> >
> > Initially I was using GadgetFS (together with the Dummy HCD/UDC module)
> > to perform emulation of USB devices for fuzzing, but later switched to a
> > custom written interface. The incentive to implement a different interface
> > was to provide a somewhat raw and direct access to the USB Gadget layer
> > for the userspace, where every USB request is passed to the userspace to
> > get a response. See documentation for the list of differences between
> > Raw Gadget and GadgetFS.
> >
> > Currently Raw Gadget only supports blocking I/O mode, that synchronously
> > waits for the result of each operation to allow collecting coverage per
> > operation.
> >
> > This patchset has been pushed to the public Linux kernel Gerrit instance:
> >
> > https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/2144
> >
> > Changes v5 -> v6:
> > - Prevent raw_process_ep_io() racing with raw_ioctl_ep_disable() by
> >   checking urb_queued flag in the latter.
> > - Use GFP_KERNEL instead of GFP_ATOMIC where possible.
> > - Reject opening raw-gadget with O_NONBLOCK to allow future extensions to
> >   support nonblocking IO.
> > - Reduce RAW_EVENT_QUEUE_SIZE to 16.
>
> Hi Felipe! I'm still hoping for a review :)
>
> (Forgot to add a link to the example that emulates a USB keyboard via
> Raw Gadget into the cover letter:
>
> https://github.com/xairy/raw-gadget/blob/master/examples/keyboard.c)

Hi Greg, Felipe, and Alan,

I was wondering if there's a way to move forward with this patch?

Alan, since you have a very good knowledge of the USB subsystem, could
I ask you to take a look at the patch, while Felipe is busy?

Thanks!

>
> >
> > Changes v4 -> v5:
> > - Specified explicit usb_raw_event_type enum values for all entries.
> > - Dropped pointless locking in gadget_unbind().
> >
> > Changes v3 -> v4:
> > - Print debug message when maxpacket check fails.
> > - Use module_misc_device() instead of module_init/exit().
> > - Reuse DRIVER_NAME macro in raw_device struct definition.
> > - Don't print WARNING in raw_release().
> > - Add comment that explains locking into raw_event_queue_fetch().
> > - Print a WARNING when event queue size is exceeded.
> > - Rename raw.c to raw_gadget.c.
> > - Mention module name in Kconfig.
> > - Reworked logging to use dev_err/dbg() instead of pr_err/debug().
> >
> > Changes v2 -> v3:
> > - Updated device path in documentation.
> > - Changed usb_raw_init struct layout to make it the same for 32 bit compat
> >   mode.
> > - Added compat_ioctl to raw_fops.
> > - Changed raw_ioctl_init() to return EINVAL for invalid USB speeds, except
> >   for USB_SPEED_UNKNOWN, which defaults to USB_SPEED_HIGH.
> > - Reject endpoints with maxpacket = 0 in raw_ioctl_ep_enable().
> >
> > Changes v1 -> v2:
> > - Moved raw.c to legacy/.
> > - Changed uapi header to use __u* types.
> > - Switched from debugfs entry to a misc device.
> > - Changed raw_dev from refcount to kref.
> > - Moved UDC_NAME_LENGTH_MAX to uapi headers.
> > - Used usb_endpoint_type() and usb_endpoint_dir_in/out() functions instead
> >   of open coding them.
> > - Added "WITH Linux-syscall-note" to SPDX id in the uapi header.
> > - Removed pr_err() if case dev_new() fails.
> > - Reduced the number of debugging messages.
> >
> > Andrey Konovalov (1):
> >   usb: gadget: add raw-gadget interface
> >
> >  Documentation/usb/index.rst            |    1 +
> >  Documentation/usb/raw-gadget.rst       |   61 ++
> >  drivers/usb/gadget/legacy/Kconfig      |   11 +
> >  drivers/usb/gadget/legacy/Makefile     |    1 +
> >  drivers/usb/gadget/legacy/raw_gadget.c | 1078 ++++++++++++++++++++++++
> >  include/uapi/linux/usb/raw_gadget.h    |  167 ++++
> >  6 files changed, 1319 insertions(+)
> >  create mode 100644 Documentation/usb/raw-gadget.rst
> >  create mode 100644 drivers/usb/gadget/legacy/raw_gadget.c
> >  create mode 100644 include/uapi/linux/usb/raw_gadget.h
> >
> > --
> > 2.25.0.265.gbab2e86ba0-goog
> >