[PATCH 1/3] pixmap: have slave pixmap take a reference on master pixmap

Dave Airlie airlied at gmail.com
Thu Aug 2 23:44:42 PDT 2012

From: Dave Airlie <airlied at redhat.com>

Since the free routines free the master pixmap then the slave, we should
be taking a reference when we bind them together.

Fixes a use-after-free when resizing a primed gears.

Signed-off-by: Dave Airlie <airlied at redhat.com>
 dix/pixmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/dix/pixmap.c b/dix/pixmap.c
index 9163e99..2418812 100644
--- a/dix/pixmap.c
+++ b/dix/pixmap.c
@@ -148,6 +148,10 @@ PixmapPtr PixmapShareToSlave(PixmapPtr pixmap, ScreenPtr slave)
                               pixmap->drawable.height, depth, 0,
                               pixmap->devKind, NULL);
+    /* have the slave pixmap take a reference on the master pixmap
+       later we destroy them both at the same time */
+    pixmap->refcnt++;
     spix->master_pixmap = pixmap;
     ret = slave->SetSharedPixmapBacking(spix, handle);

More information about the xorg-devel mailing list