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From:   John Boero <boeroboy@gmail.com>
Date:   Fri, 13 Nov 2020 16:45:52 +0000
Message-ID: <CAO5W59iqXGeAQTP7hzzRmbqwZUcK=vwuJ7pFzzNzZ9o11_k2tw@mail.gmail.com>
Subject: Re: [PATCH] usb: core: Null deref in kernel with USB webcams.
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Felipe Balbi <balbi@kernel.org>, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Sorry I wanted to include a pastebin or link but was trying to follow maillist
guidelines and not include links or exceed wrap guidelines.  Full contents:
https://paste.centos.org/view/3746bc40

Yes I understand the return dodges the config dereference.

Original line usb.c:281 is the original error:

280| for (i = 0; i < config->desc.bNumInterfaces; i++)
281|  if (config->interface[i]->altsetting[0]
282|    .desc.bInterfaceNumber == ifnum)
283|  return config->interface[i];

Thanks
John

On Fri, Nov 13, 2020 at 4:34 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Fri, Nov 13, 2020 at 01:18:05PM +0000, John Boero wrote:
> > Thanks for the tips.
> >
> > I've spent some more time on this this morning.
> > It looks like it's not the dev after all.
>
> What isn't the dev?
>
> > Every interface in the dev is set NULL after init.
>
> I can't tell what this means.  Please be more explicit.
>
> > Just like in the original Ubuntu bug 1827452 filed by someone else
> > the device seems to disconnect itself after uvcvideo initialization.
> > Then there is a 5 second pause before usb_ifnum_to_if tries
> > to iterate through its 8 interfaces - all of which are null.
> > It looks like uvc properly locks the dev, so maybe this could
> > be caused by any device being unplugged after init?
>
> More likely there is a bug in the uvcvideo driver.
>
> > The WARNING handle preserves USB function though,
> > and subsequent lsusb behaves fine:
>
> No, the WARN only writes a message to the system log.  The "return"
> statement is what prevented the system from crashing.
>
> > $ lsusb | fold -w 80
> > Bus 002 Device 002: ID 8087:8002 Intel Corp. 8 channel internal hub
> > Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> > Bus 001 Device 002: ID 8087:800a Intel Corp. Hub
> > Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> > Bus 004 Device 002: ID 0451:8140 Texas Instruments, Inc. TUSB8041 4-Port Hub
> > Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> > Bus 003 Device 005: ID 1ea7:0064 SHARKOON Technologies GmbH 2.4GHz Wireless rech
> > argeable vertical mouse [More&Better]
> > Bus 003 Device 004: ID 145f:025c Trust Trust USB Microphone
> > Bus 003 Device 002: ID 1050:0407 Yubico.com Yubikey 4/5 OTP+U2F+CCID
> > Bus 003 Device 009: ID 0a5c:21e8 Broadcom Corp. BCM20702A0 Bluetooth 4.0
> > Bus 003 Device 008: ID 0451:8142 Texas Instruments, Inc. TUSB8041 4-Port Hub
> > Bus 003 Device 006: ID 062a:4101 MosArt Semiconductor Corp. Wireless Keyboard/Mo
> > use
> > Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> > Bus 006 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> > Bus 005 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> >
> > 8x (0-7) occurences of the following WARNING:
> >
> > [ 140.678756] usb 3-4: USB disconnect, device number 3
> > [ 145.995855] ------------[ cut here ]------------
> > [ 145.995863] dev interface is NULL in usb_ifnum_to_if
> > [ 145.995907] WARNING: CPU: 31 PID: 5617 at drivers/usb/core/usb.c:289
> > usb_ifnum_to_if+0x58/0x80
>
> You removed the most important part of the log message!  What appears
> below this point?
>
> In fact, you should just post the entire log (or put it on a server
> somewhere and post a URL).
>
> Alan Stern