From 59ad0e6a416d8e23f9d962af67a16ee28ec7867b Mon Sep 17 00:00:00 2001 From: Olivier Fourdan Date: Wed, 30 Nov 2016 09:42:43 +0100 Subject: [PATCH] xwayland: Fix use after free of cursors MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sometimes, Xwayland will try to use a cursor that has just been freed, leading to a crash when trying to access that cursor data either in miPointerUpdateSprite() or AnimCurTimerNotify(). CheckMotion() updates the pointer's cursor based on which xwindow XYToWindow() returns, and Xwayland implements its own xwl_xy_to_window() to fake a crossing to the root window when the pointer has left the Wayland surface but is still within the xwindow. But after an xwindow is unrealized, the last xwindow used to match the xwindows is cleared so two consecutive calls to xwl_xy_to_window() may not return the same xwindow. To avoid this issue, update the last_xwindow based on enter and leave notifications instead of xwl_xy_to_window(), and check if the xwindow found by the regular miXYToWindow() is a child of the known last xwindow, so that multiple consecutive calls to xwl_xy_to_window() return the same xwindow, being either the one found by miXYToWindow() or the root window. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1385258 Signed-off-by: Olivier Fourdan Tested-by: Vít Ondruch Tested-by: Satish Balay Reviewed-by: Jonas Ådahl --- hw/xwayland/xwayland-input.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/hw/xwayland/xwayland-input.c b/hw/xwayland/xwayland-input.c index 3bc711082..580df09b9 100644 --- a/hw/xwayland/xwayland-input.c +++ b/hw/xwayland/xwayland-input.c @@ -312,6 +312,9 @@ pointer_handle_enter(void *data, struct wl_pointer *pointer, dx = xwl_seat->focus_window->window->drawable.x; dy = xwl_seat->focus_window->window->drawable.y; + /* We just entered a new xwindow, forget about the old last xwindow */ + xwl_seat->last_xwindow = NullWindow; + master = GetMaster(dev, POINTER_OR_FLOAT); (*pScreen->SetCursorPosition) (dev, pScreen, dx + sx, dy + sy, TRUE); @@ -360,8 +363,14 @@ pointer_handle_leave(void *data, struct wl_pointer *pointer, xwl_seat->xwl_screen->serial = serial; - xwl_seat->focus_window = NULL; - CheckMotion(NULL, GetMaster(dev, POINTER_OR_FLOAT)); + /* The pointer has left a known xwindow, save it for a possible match + * in sprite_check_lost_focus() + */ + if (xwl_seat->focus_window) { + xwl_seat->last_xwindow = xwl_seat->focus_window->window; + xwl_seat->focus_window = NULL; + CheckMotion(NULL, GetMaster(dev, POINTER_OR_FLOAT)); + } } static void @@ -1252,10 +1261,10 @@ sprite_check_lost_focus(SpritePtr sprite, WindowPtr window) */ if (master->lastSlave == xwl_seat->pointer && xwl_seat->focus_window == NULL && - xwl_seat->last_xwindow == window) + xwl_seat->last_xwindow != NullWindow && + IsParent(xwl_seat->last_xwindow, window)) return TRUE; - xwl_seat->last_xwindow = window; return FALSE; }