Re: [PATCH] staging: speakup: fix wraparound in uaccess length check

[Jann Horn]

On Sat, Jul 7, 2018 at 7:03 AM Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Sat, Jul 07, 2018 at 10:29:26AM +0200, Samuel Thibault wrote:
> > Re,
> >
> > Could you review, test, and resubmit the patch below instead?
> >
> > Samuel
> >
> >
> > 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.
> >
> > Fixes: 425e586cf95b ("speakup: add unicode variant of /dev/softsynth")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
>
> You forgot a "reported-by:" line :(
>
> also, I already applied Jann's patch, so could you either just send the
> fixup, or a revert/add of this patch once you all agree on the proper
> solution here?

I think my patch was garbage (as both Samuel and Dan Carpenter's
smatch warning pointed out) and should be reverted. Should I be
sending the revert?