saa: Make sure damage destruction happens at the correct location

Incorrect DestroyPixmap wrapping previously made the destruction of damage
objects typically happen in damageDestroyPixmap(), leaving a dangling
damage pointer in saa_destroy_pixmap() which was only cleared. However in
some cases that caused us to leak damage objects.

Rework saa initialization somewhat to make sure saa_destroy_pixmap happens
before damageDestroyPixmap and destroy the damage object in saa_destroy_pixmap.
Also add a damage object destruction notifier callback that clears the
saa pixmap damage pointer should the damage object destruction accidentally
happen elsewhere.

This makes sure we don't leak damage objects.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>

1 files changed, 63 insertions, 9 deletions

diff --git a/saa/saa.c b/saa/saa.c
index be9520e..0d88256 100644
--- a/saa/saa.c
+++ b/saa/saa.c
@@ -216,6 +216,27 @@ saa_report_damage(DamagePtr damage, RegionPtr reg, void *closure)
     DamageEmpty(damage);
 }
 
+/**
+ * saa_notify_destroy_damage - Handle destroy damage notification
+ *
+ * \param damage[in] damage Pointer to damage about to be destroyed
+ * \param closure[in] closure Closure.
+ *
+ * Makes sure that whatever code destroys a damage object clears the
+ * saa_pixmap damage pointer. This is extra protection. Typically
+ * saa_destroy_pixmap should be correct if the various subsystem
+ * DestroyPixmap functions are called in the right order.
+ */
+static void
+saa_notify_destroy_damage(DamagePtr damage, void *closure)
+{
+    PixmapPtr pixmap = (PixmapPtr) closure;
+    struct saa_pixmap *spix = saa_get_saa_pixmap(pixmap);
+
+    if (spix->damage == damage)
+	spix->damage = NULL;
+}
+
 Bool
 saa_add_damage(PixmapPtr pixmap)
 {
@@ -225,7 +246,7 @@ saa_add_damage(PixmapPtr pixmap)
     if (spix->damage)
 	return TRUE;
 
-    spix->damage = DamageCreate(saa_report_damage, NULL,
+    spix->damage = DamageCreate(saa_report_damage, saa_notify_destroy_damage,
 				DamageReportRawRegion, TRUE, pScreen, pixmap);
     if (!spix->damage)
 	return FALSE;
@@ -590,14 +611,15 @@ saa_set_fallback_debug(ScreenPtr screen, Bool enable)
 }
 
 /**
- * saa_close_screen() unwraps its wrapped screen functions and tears down SAA's
- * screen private, before calling down to the next CloseScreen.
+ * saa_early_close_screen() Makes sure we call saa_destroy_pixmap on the
+ * miScreenInit() pixmap _before_ damageCloseScreen, after which it will
+ * generate an invalid memory access. Also unwraps the functions we
+ * wrapped _after_ DamageSetup().
  */
-Bool
-saa_close_screen(CLOSE_SCREEN_ARGS_DECL)
+static Bool
+saa_early_close_screen(CLOSE_SCREEN_ARGS_DECL)
 {
     struct saa_screen_priv *sscreen = saa_screen(pScreen);
-    struct saa_driver *driver = sscreen->driver;
 
     if (pScreen->devPrivate) {
 	/* Destroy the pixmap created by miScreenInit() *before*
@@ -609,11 +631,26 @@ saa_close_screen(CLOSE_SCREEN_ARGS_DECL)
 	pScreen->devPrivate = NULL;
     }
 
+    saa_unwrap_early(sscreen, pScreen, CloseScreen);
+    saa_unwrap(sscreen, pScreen, DestroyPixmap);
+
+    return (*pScreen->CloseScreen) (CLOSE_SCREEN_ARGS);
+}
+
+/**
+ * saa_close_screen() unwraps its wrapped screen functions and tears down SAA's
+ * screen private, before calling down to the next CloseScreen.
+ */
+Bool
+saa_close_screen(CLOSE_SCREEN_ARGS_DECL)
+{
+    struct saa_screen_priv *sscreen = saa_screen(pScreen);
+    struct saa_driver *driver = sscreen->driver;
+
     saa_unwrap(sscreen, pScreen, CloseScreen);
     saa_unwrap(sscreen, pScreen, CreateGC);
     saa_unwrap(sscreen, pScreen, ChangeWindowAttributes);
     saa_unwrap(sscreen, pScreen, CreatePixmap);
-    saa_unwrap(sscreen, pScreen, DestroyPixmap);
     saa_unwrap(sscreen, pScreen, ModifyPixmapHeader);
     saa_unwrap(sscreen, pScreen, BitmapToRegion);
 #ifdef RENDER
@@ -726,15 +763,32 @@ saa_driver_init(ScreenPtr screen, struct saa_driver * saa_driver)
     saa_wrap(sscreen, screen, ChangeWindowAttributes,
 	     saa_change_window_attributes);
     saa_wrap(sscreen, screen, CreatePixmap, saa_create_pixmap);
-    saa_wrap(sscreen, screen, DestroyPixmap, saa_destroy_pixmap);
     saa_wrap(sscreen, screen, ModifyPixmapHeader, saa_modify_pixmap_header);
-
     saa_wrap(sscreen, screen, BitmapToRegion, saa_bitmap_to_region);
     saa_unaccel_setup(screen);
 #ifdef RENDER
     saa_render_setup(screen);
 #endif
 
+    /*
+     * Correct saa functionality relies on Damage, so set it up now.
+     * Note that this must happen _after_ wrapping the rendering functionality
+     * so that damage happens outside of saa.
+     */
+    if (!DamageSetup(screen))
+	return FALSE;
+
+    /*
+     * Wrap DestroyPixmap after DamageSetup, so that saa_destroy_pixmap is
+     * called _before_ damageDestroyPixmap. This is to make damageDestroyPixmap
+     * doesn't free objects pointed to by our damage pointers.
+     *
+     * Also wrap an early CloseScreen to perform actions needed to be done
+     * before damageCloseScreen and to unwrap DestroyPixmap correctly.
+     */
+    saa_wrap(sscreen, screen, DestroyPixmap, saa_destroy_pixmap);
+    saa_wrap_early(sscreen, screen, CloseScreen, saa_early_close_screen);
+
     return TRUE;
 }