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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jann Horn <jannh@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	devel@driverdev.osuosl.org, kirk@reisers.ca,
	speakup@linux-speakup.org,
	kernel list <linux-kernel@vger.kernel.org>,
	Samuel Thibault <samuel.thibault@ens-lyon.org>,
	Christopher Brannon <chris@the-brannons.com>
Subject: Re: [PATCH] staging: speakup: fix wraparound in uaccess length check
Date: Fri, 13 Jul 2018 10:31:54 +0200	[thread overview]
Message-ID: <20180713083154.GA21160@kroah.com> (raw)
In-Reply-To: <CAG48ez0ZLzh1L8HieUJ+UmbQewRMc_0hwJG7-MB=WR1h=VagZA@mail.gmail.com>

On Thu, Jul 12, 2018 at 04:12:39PM -0700, Jann Horn wrote:
> On Thu, Jul 12, 2018 at 3:47 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > On Fri, Jul 13, 2018 at 12:29:36AM +0200, Jann Horn wrote:
> > > From: Samuel Thibault <samuel.thibault@ens-lyon.org>
> > >
> > > From: Samuel Thibault <samuel.thibault@ens-lyon.org>
> > >
> > > If softsynthx_read() is called with `count < 3`, `count - 3` wraps, causing
> > > the loop to copy as much data as available to the provided buffer. If
> > > softsynthx_read() is invoked through sys_splice(), this causes an
> > > unbounded kernel write; but even when userspace just reads from it
> > > normally, a small size could cause userspace crashes.
> >
> > Or you could try this (completely untested, though):
> 
> I think this has the same problem as my original buggy patch: At the
> point where you notice that you'd overflow the buffer, you've already
> consumed a character from the synth buffer. You'd have to put it back,
> and since the spinlock protecting it has been dropped, that's a bit
> weird.
> 
> Also, I'm not sure whether Greg prefers fixes for stable kernels that
> don't also contain cleanup?

For staging code, I really don't care, as long as it's fixing an issue :)

thanks,

greg k-h

  reply	other threads:[~2018-07-13  8:32 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-12 22:29 [PATCH] staging: speakup: fix wraparound in uaccess length check Jann Horn
2018-07-12 22:47 ` Al Viro
2018-07-12 23:12   ` Jann Horn
2018-07-13  8:31     ` Greg Kroah-Hartman [this message]
  -- strict thread matches above, loose matches on Subject: below --
2018-07-07  1:53 Jann Horn
2018-07-07  8:01 ` Greg Kroah-Hartman
2018-07-07  8:13 ` Samuel Thibault
2018-07-07  8:22   ` Jann Horn
2018-07-07  8:32     ` Samuel Thibault
2018-07-07  8:29 ` Samuel Thibault
2018-07-07 14:03   ` Greg Kroah-Hartman
2018-07-10 20:34     ` Jann Horn
2018-07-11  9:27       ` Greg Kroah-Hartman
2018-07-10 20:34   ` Jann Horn
2018-07-11  9:44     ` Samuel Thibault

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