[PATCH 1.9.2.902 1/1] dix: GetPointerEvents: added valuator range checking

[Peter Hutterer]

On Mon, Jan 24, 2011 at 10:03:30PM +0200, Oliver McFadden wrote:
> Button events may be sent with no valuators (e.g. to simply indicate
> ButtonPress or ButtonRelease without any coordinates); when this happens
> the server would read uninitialized memory.
> 
> ==9999== Conditional jump or move depends on uninitialised value(s)
> ==9999==    at 0x48E87E8: pixman_f_transform_point (in /usr/lib/libpixman-1.so.0.18.2)
> ==9999==  Uninitialised value was created by a stack allocation
> ==9999==    at 0x37524: GetPointerEvents (getevents.c:1074)
> ==9999==
> ==9999== Conditional jump or move depends on uninitialised value(s)
> ==9999==    at 0x496D074: lround (s_lround.c:40)
> ==9999==    by 0x3773B: GetPointerEvents (getevents.c:1048)
> ==9999==    by 0x683BB: xf86PostButtonEventP (xf86Xinput.c:1162)
> ==9999==    by 0x6853B: xf86PostButtonEvent (xf86Xinput.c:1126)
> ==9999==    by 0x5779037: process_state (multitouch.c:321)      (xf86-input-mtev)
> ==9999==    by 0x577908F: read_input (multitouch.c:331))        (xf86-input-mtev)
> ==9999==    by 0x66B4F: xf86SigioReadInput (xf86Events.c:298)
> ==9999==    by 0x112697: xf86SIGIO (sigio.c:118)
> ==9999==    by 0x4A12B2F: ??? (sigrestorer.S:51)
> ==9999==  Uninitialised value was created by a stack allocation
> ==9999==    at 0x37524: GetPointerEvents (getevents.c:1074)
> 
> Signed-off-by: Oliver McFadden <oliver.mcfadden at nokia.com>

Reviewed-by: Peter Hutterer <peter.hutterer at who-t.net>

Jeremy, feel free to pick this up

Cheers,
  Peter
> ---
> I'm not sure anyone actually cares about this patch anymore, since this code has
> changed completely due to the valuator rework. If someone wants to apply it to
> the 1.9.2(.xxx) branches, then please be my guest.
> 
>  dix/getevents.c |   18 ++++++++++--------
>  1 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/dix/getevents.c b/dix/getevents.c
> index e5134d3..f1e5514 100644
> --- a/dix/getevents.c
> +++ b/dix/getevents.c
> @@ -1034,19 +1034,21 @@ FreeEventList(EventListPtr list, int num_events)
>  }
>  
>  static void
> -transformAbsolute(DeviceIntPtr dev, int v[MAX_VALUATORS])
> +transformAbsolute(DeviceIntPtr dev, int first, int num, int *valuators)
>  {
> -    struct pixman_f_vector p;
> +    struct pixman_f_vector p = { .v = {0.0, 0.0, 1.0} };
>  
>      /* p' = M * p in homogeneous coordinates */
> -    p.v[0] = v[0];
> -    p.v[1] = v[1];
> -    p.v[2] = 1.0;
> +    if (num >= 1 && first == 0)
> +        p.v[0] = *(valuators + 0);
> +
> +    if (first <= 1 && num >= (2 - first))
> +        p.v[1] = *(valuators + 1 - first);
>  
>      pixman_f_transform_point(&dev->transform, &p);
>  
> -    v[0] = lround(p.v[0]);
> -    v[1] = lround(p.v[1]);
> +    valuators[0] = lround(p.v[0]);
> +    valuators[1] = lround(p.v[1]);
>  }
>  
>  /**
> @@ -1124,7 +1126,7 @@ GetPointerEvents(EventList *events, DeviceIntPtr pDev, int type, int buttons,
>                          scr->height);
>          }
>  
> -        transformAbsolute(pDev, valuators);
> +        transformAbsolute(pDev, first_valuator, num_valuators, valuators);
>          moveAbsolute(pDev, &x, &y, first_valuator, num_valuators, valuators);
>      } else {
>          if (flags & POINTER_ACCELERATE) {
> -- 
> 1.7.1.245.g7c42e
>