Xi: get device changed data from DeviceChangedEvents, not the device (#23100)

If a new device posts an event while the DCE is in the queue, getting the
data from the device may result in invalid memory access.

X.Org Bug 23100 <http://bugs.freedesktop.org/show_bug.cgi?id=23100>

1 files changed, 66 insertions, 3 deletions

diff --git a/Xi/exevents.c b/Xi/exevents.c
index 85d14b09b..49eacb4d1 100644
--- a/Xi/exevents.c
+++ b/Xi/exevents.c
@@ -674,6 +674,69 @@ DeepCopyDeviceClasses(DeviceIntPtr from, DeviceIntPtr to, DeviceChangedEvent *dc
 }
 
 
+static int
+AppendKeyInfo(DeviceChangedEvent *dce, xXIKeyInfo* info)
+{
+    uint32_t *kc;
+    int i;
+
+    info->type = KeyClass;
+    info->num_keycodes = dce->keys.max_keycode - dce->keys.min_keycode + 1;
+    info->length = sizeof(xXIKeyInfo)/4 + info->num_keycodes;
+    info->sourceid = dce->deviceid;
+
+    kc = (uint32_t*)&info[1];
+    for (i = 0; i < info->num_keycodes; i++)
+        *kc++ = i + dce->keys.min_keycode;
+
+    return info->length * 4;
+}
+
+static int
+AppendButtonInfo(DeviceChangedEvent *dce, xXIButtonInfo *info)
+{
+    unsigned char *bits;
+    int mask_len;
+
+    mask_len = bytes_to_int32(bits_to_bytes(dce->buttons.num_buttons));
+
+    info->type = ButtonClass;
+    info->num_buttons = dce->buttons.num_buttons;
+    info->length = bytes_to_int32(sizeof(xXIButtonInfo)) +
+                   info->num_buttons + mask_len;
+    info->sourceid = dce->deviceid;
+
+    bits = (unsigned char*)&info[1];
+    memset(bits, 0, mask_len * 4);
+    /* FIXME: is_down? */
+
+    bits += mask_len * 4;
+    memcpy(bits, dce->buttons.names, dce->buttons.num_buttons * sizeof(Atom));
+
+    return info->length * 4;
+}
+
+static int
+AppendValuatorInfo(DeviceChangedEvent *dce, xXIValuatorInfo *info, int axisnumber)
+{
+    info->type = ValuatorClass;
+    info->length = sizeof(xXIValuatorInfo)/4;
+    info->label = dce->valuators[axisnumber].name;
+    info->min.integral = dce->valuators[axisnumber].min;
+    info->min.frac = 0;
+    info->max.integral = dce->valuators[axisnumber].max;
+    info->max.frac = 0;
+    /* FIXME: value */
+    info->value.integral = 0;
+    info->value.frac = 0;
+    info->resolution = dce->valuators[axisnumber].resolution;
+    info->number = axisnumber;
+    info->mode = dce->valuators[axisnumber].mode; /* Server doesn't have per-axis mode yet */
+    info->sourceid = dce->deviceid;
+
+    return info->length * 4;
+}
+
 /**
  * Send an XI2 DeviceChangedEvent to all interested clients.
  */
@@ -723,13 +786,13 @@ XISendDeviceChangedEvent(DeviceIntPtr device, DeviceIntPtr master, DeviceChanged
     if (dce->buttons.num_buttons)
     {
         dcce->num_classes++;
-        ptr += ListButtonInfo(device, (xXIButtonInfo*)ptr);
+        ptr += AppendButtonInfo(dce, (xXIButtonInfo*)ptr);
     }
 
     if (nkeys)
     {
         dcce->num_classes++;
-        ptr += ListKeyInfo(device, (xXIKeyInfo*)ptr);
+        ptr += AppendKeyInfo(dce, (xXIKeyInfo*)ptr);
     }
 
     if (dce->num_valuators)
@@ -738,7 +801,7 @@ XISendDeviceChangedEvent(DeviceIntPtr device, DeviceIntPtr master, DeviceChanged
 
         dcce->num_classes += dce->num_valuators;
         for (i = 0; i < dce->num_valuators; i++)
-            ptr += ListValuatorInfo(device, (xXIValuatorInfo*)ptr, i);
+            ptr += AppendValuatorInfo(dce, (xXIValuatorInfo*)ptr, i);
     }
 
     /* we don't actually swap if there's a NullClient, swapping is done