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xwayland: Restrict allow commit to the window manager 

Xwayland offers a way for the window and compositing manager to hold the
surface commits through an X11 property _XWAYLAND_ALLOW_COMMITS.

Xwayland, however, does not actually check if the X11 client changing
the value of that property is indeed the X11 window manager, so any X11
client can potentially interfere with the Wayland surface mechanism.

Restrict access to the _XWAYLAND_ALLOW_COMMITS property to read-only,
except for the X11 window manager and the Xserver itself.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.com>
This commit is contained in:
Olivier Fourdan 2023-11-08 13:53:48 +01:00 committed by Olivier Fourdan
parent a07c2cda98
commit 2cc869626a
1 changed files with 21 additions and 0 deletions
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21
hw/xwayland/xwayland-screen.c
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@ -167,12 +167,33 @@ xwl_property_callback(CallbackListPtr *pcbl, void *closure,
xwl_window_update_property(xwl_window, rec);
}
#define readOnlyPropertyAccessMask (DixReadAccess |\
DixGetAttrAccess |\
DixListPropAccess |\
DixGetPropAccess)
static void
xwl_access_property_callback(CallbackListPtr *pcbl, void *closure,
void *calldata)
{
XacePropertyAccessRec *rec = calldata;
PropertyPtr prop = *rec->ppProp;
ClientPtr client = rec->client;
Mask access_mode = rec->access_mode;
ScreenPtr pScreen = closure;
struct xwl_screen *xwl_screen = xwl_screen_get(pScreen);
if (prop->propertyName == xwl_screen->allow_commits_prop) {
/* Only the WM and the Xserver itself */
if (client != serverClient &&
client->index != xwl_screen->wm_client_id &&
(access_mode & ~readOnlyPropertyAccessMask) != 0)
rec->status = BadAccess;
}
}
#undef readOnlyPropertyAccessMask
static void
xwl_root_window_finalized_callback(CallbackListPtr *pcbl,
void *closure,