linux-kernel - Re: [PATCH AUTOSEL 4.19 592/671] USB: usb-skeleton: fix use-after-free after driver unbind

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Message-ID: <20200123142617.GA1685167@kroah.com>
Date:   Thu, 23 Jan 2020 15:26:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Johan Hovold <johan@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.19 592/671] USB: usb-skeleton: fix
 use-after-free after driver unbind

On Thu, Jan 23, 2020 at 09:22:52AM -0500, Sasha Levin wrote:
> On Fri, Jan 17, 2020 at 11:21:16AM +0100, Johan Hovold wrote:
> > On Thu, Jan 16, 2020 at 12:03:50PM -0500, Sasha Levin wrote:
> > > From: Johan Hovold <johan@...nel.org>
> > > 
> > > [ Upstream commit 6353001852776e7eeaab4da78922d4c6f2b076af ]
> > > 
> > > The driver failed to stop its read URB on disconnect, something which
> > > could lead to a use-after-free in the completion handler after driver
> > > unbind in case the character device has been closed.
> > > 
> > > Fixes: e7389cc9a7ff ("USB: skel_read really sucks royally")
> > > Signed-off-by: Johan Hovold <johan@...nel.org>
> > > Link: https://lore.kernel.org/r/20191009170944.30057-3-johan@kernel.org
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Signed-off-by: Sasha Levin <sashal@...nel.org>
> > 
> > This one isn't needed in any stable tree. As we discussed before, the
> > skeleton driver is only there for documentation purposes.
> 
> I'll drop this, but I'm curious: doesn't this mean that users will build
> on buggy example code?

They should always be grabbing the "latest" version of the file to work
off of anyway.  Given that there are very few new USB drivers anymore, I
doubt this really matters much...

thanks,

greg k-h