[PATCH libXi] Force class alignment to a multiple of sizeof(XID).

[Peter Hutterer]

On Tue, Jan 17, 2012 at 09:26:14PM +0100, Matthieu Herrb wrote:
> From: Peter Hutterer <peter.hutterer at who-t.net>
> 
> Calculate length field to a multiples of sizeof(XID). XIDs are typedefs
> to ulong and thus may be 8 bytes on some platforms. This can trigger a
> SIGBUS if a class ends up not being 8-aligned (e.g. after XAxisInfo).
> 
> Reported-by: Nicolai Stange <nicolai.stange at zmaw.de>
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> Signed-off-by: Matthieu Herrb <matthieu.herrb at laas.fr>

   15feb92..07ced7b  master -> master

thanks.

Cheers,
  Peter

> ---
>  src/XListDev.c |   27 +++++++++++++++++++--------
>  1 files changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/src/XListDev.c b/src/XListDev.c
> index 6a16da4..6b91238 100644
> --- a/src/XListDev.c
> +++ b/src/XListDev.c
> @@ -61,6 +61,17 @@ SOFTWARE.
>  #include <X11/extensions/extutil.h>
>  #include "XIint.h"
>  
> +/* Calculate length field to a multiples of sizeof(XID). XIDs are typedefs
> + * to ulong and thus may be 8 bytes on some platforms. This can trigger a
> + * SIGBUS if a class ends up not being 8-aligned (e.g. after XAxisInfo).
> + */
> +static int pad_to_xid(int base_size)
> +{
> +    int padsize = sizeof(XID);
> +
> +    return ((base_size + padsize - 1)/padsize) * padsize;
> +}
> +
>  static int
>  SizeClassInfo(xAnyClassPtr *any, int num_classes)
>  {
> @@ -69,18 +80,18 @@ SizeClassInfo(xAnyClassPtr *any, int num_classes)
>      for (j = 0; j < num_classes; j++) {
>          switch ((*any)->class) {
>              case KeyClass:
> -                size += sizeof(XKeyInfo);
> +                size += pad_to_xid(sizeof(XKeyInfo));
>                  break;
>              case ButtonClass:
> -                size += sizeof(XButtonInfo);
> +                size += pad_to_xid(sizeof(XButtonInfo));
>                  break;
>              case ValuatorClass:
>                  {
>                      xValuatorInfoPtr v;
>  
>                      v = (xValuatorInfoPtr) *any;
> -                    size += sizeof(XValuatorInfo) +
> -                        (v->num_axes * sizeof(XAxisInfo));
> +                    size += pad_to_xid(sizeof(XValuatorInfo) +
> +                        (v->num_axes * sizeof(XAxisInfo)));
>                      break;
>                  }
>              default:
> @@ -105,7 +116,7 @@ ParseClassInfo(xAnyClassPtr *any, XAnyClassPtr *Any, int num_classes)
>                      xKeyInfoPtr k = (xKeyInfoPtr) *any;
>  
>                      K->class = KeyClass;
> -                    K->length = sizeof(XKeyInfo);
> +                    K->length = pad_to_xid(sizeof(XKeyInfo));
>                      K->min_keycode = k->min_keycode;
>                      K->max_keycode = k->max_keycode;
>                      K->num_keys = k->num_keys;
> @@ -117,7 +128,7 @@ ParseClassInfo(xAnyClassPtr *any, XAnyClassPtr *Any, int num_classes)
>                      xButtonInfoPtr b = (xButtonInfoPtr) *any;
>  
>                      B->class = ButtonClass;
> -                    B->length = sizeof(XButtonInfo);
> +                    B->length = pad_to_xid(sizeof(XButtonInfo));
>                      B->num_buttons = b->num_buttons;
>                      break;
>                  }
> @@ -129,8 +140,8 @@ ParseClassInfo(xAnyClassPtr *any, XAnyClassPtr *Any, int num_classes)
>                      xAxisInfoPtr a;
>  
>                      V->class = ValuatorClass;
> -                    V->length = sizeof(XValuatorInfo) +
> -                        (v->num_axes * sizeof(XAxisInfo));
> +                    V->length = pad_to_xid(sizeof(XValuatorInfo) +
> +                        (v->num_axes * sizeof(XAxisInfo)));
>                      V->num_axes = v->num_axes;
>                      V->motion_buffer = v->motion_buffer_size;
>                      V->mode = v->mode;
> -- 
> 1.7.6
> 
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