On Mon, Jan 30, 2023 at 11:55:18PM +0100, Philippe Mathieu-Daudé wrote:
> On 30/1/23 14:50, Akihiko Odaki wrote:
> > The expiration time provided for timer_mod() can overflow if a
> > ridiculously large value is set to the comparator register. The
> > resulting value can represent a past time after rounded, forcing the
> > timer to fire immediately. If the timer is configured as periodic, it
> > will rearm the timer again, and form an endless loop.
> >
> > Check if the expiration value will overflow, and if it will, stop the
> > timer instead of rearming the timer with the overflowed time.
> >
> > This bug was found by Alexander Bulekov when fuzzing igb, a new
> > network device emulation:
> > https://patchew.org/QEMU/20230129053316.1071513-1-alx...@bu.edu/
> >
> > The fixed test case is:
> > fuzz/crash_2d7036941dcda1ad4380bb8a9174ed0c949bcefd
> >
> > Fixes: 16b29ae180 ("Add HPET emulation to qemu (Beth Kon)")
> > Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
> > ---
> > hw/timer/hpet.c | 19 +++++++++++++------
> > 1 file changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c
> > index 9520471be2..3657d5f463 100644
> > --- a/hw/timer/hpet.c
> > +++ b/hw/timer/hpet.c
> > @@ -352,6 +352,16 @@ static const VMStateDescription vmstate_hpet = {
> > }
> > };
> > +static void arm(HPETTimer *t, uint64_t ticks)
>
> Could we rename as hpet_[re]arm() similarly to this file's other helpers?
Akihiko Odaki, I expect there will be a new version of this?
> > +{
> > + if (ticks < ns_to_ticks(INT64_MAX / 2)) {
> > + timer_mod(t->qemu_timer,
> > + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
> > ticks_to_ns(ticks));
> > + } else {
> > + timer_del(t->qemu_timer);
> > + }
> > +}
