[PATCH qxl] qxl: Initialize prev field while dup surface list

[Victor Toso]

From: Victor Toso <me at victortoso.com>

Otherwise we will can hit a segfault qxl_surface_kill()

 │717     void
 │718     qxl_surface_kill (qxl_surface_t *surface)
 │719     {
 │720         struct evacuated_surface_t *ev = surface->evacuated;
 │721
 │722         if (ev)
 │723         {
 │724             /* server side surface is already destroyed (via reset), don't
 │725              * resend a destroy. Just mark surface as not to be recreated */
 │726             ev->pixmap = NULL;│
 │727             if (ev->image)│
 │728                 pixman_image_unref (ev->image);
 │729             if (ev->next)
 │730                 ev->next->prev = ev->prev;
 │731             if (ev->prev)
>│732                ev->prev->next = ev->next;
 │733             free(ev);
 │734             surface->evacuated = NULL;
 │735             return;
 │736         }

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1641793

Signed-off-by: Victor Toso <victortoso at redhat.com>
---
 src/qxl_surface_ums.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/qxl_surface_ums.c b/src/qxl_surface_ums.c
index 2c16ede..19cbd36 100644
--- a/src/qxl_surface_ums.c
+++ b/src/qxl_surface_ums.c
@@ -792,6 +792,7 @@ qxl_surface_cache_evacuate_all (surface_cache_t *cache)
 
 	unlink_surface (s);
 	
+	evacuated->prev = NULL;
 	evacuated->next = evacuated_surfaces;
         if (evacuated_surfaces)
             evacuated_surfaces->prev = evacuated;
-- 
2.17.2