privates: Clear screen-specific keys during CloseScreen

The modesetting driver corrupts memory when used after a server regeneration
because not enough memory is allocated for its pixmap privates.  This happens
because its call to dixRegisterScreenSpecificPrivateKey() does nothing because
key->initialized is still TRUE from the first server generation.  However, the
key is not in the screen's linked list of screen-specific privates because
that's freed and reallocated during the server generation loop in dix_main().

Fix this by clearing key->initialized before CloseScreen and add a call to
dixFreeScreenSpecificPrivates() for GPU screens.

v2: Just set key->initialized to FALSE and move dixFreeScreenSpecificPrivates()
calls to after CloseScreen.

v3: Move dixFreeScreenSpecificPrivates() calls back to just before CloseScreen.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Keith Packard <keithp@keithp.com>

dix/main.c

@@ -339,6 +339,7 @@ dix_main(int argc, char *argv[], char *envp[])
         for (i = screenInfo.numGPUScreens - 1; i >= 0; i--) {
             ScreenPtr pScreen = screenInfo.gpuscreens[i];
             FreeScratchPixmapsForScreen(pScreen);
+            dixFreeScreenSpecificPrivates(pScreen);
             (*pScreen->CloseScreen) (pScreen);
             dixFreePrivates(pScreen->devPrivates, PRIVATE_SCREEN);
             free(pScreen);

dix/privates.c

@@ -642,6 +642,15 @@ dixRegisterScreenSpecificPrivateKey(ScreenPtr pScreen, DevPrivateKey key,
 void
 dixFreeScreenSpecificPrivates(ScreenPtr pScreen)
 {
+    DevPrivateType t;
+
+    for (t = PRIVATE_XSELINUX; t < PRIVATE_LAST; t++) {
+        DevPrivateKey key;
+
+        for (key = pScreen->screenSpecificPrivates[t].key; key; key = key->next) {
+            key->initialized = FALSE;
+        }
+    }
 }
 
 /* Initialize screen-specific privates in AddScreen */