From d6c7de9eadca980c8ce3b3b7752b67bfa95e6f31 Mon Sep 17 00:00:00 2001 From: Peter Hutterer Date: Tue, 29 Nov 2022 14:53:07 +1000 Subject: [PATCH] Xext: free the screen saver resource when replacing it This fixes a use-after-free bug: When a client first calls ScreenSaverSetAttributes(), a struct ScreenSaverAttrRec is allocated and added to the client's resources. When the same client calls ScreenSaverSetAttributes() again, a new struct ScreenSaverAttrRec is allocated, replacing the old struct. The old struct was freed but not removed from the clients resources. Later, when the client is destroyed the resource system invokes ScreenSaverFreeAttr and attempts to clean up the already freed struct. Fix this by letting the resource system free the old attrs instead. CVE-2022-46343, ZDI-CAN 19404 This vulnerability was discovered by: Jan-Niklas Sohn working with Trend Micro Zero Day Initiative Signed-off-by: Peter Hutterer Acked-by: Olivier Fourdan (cherry picked from commit 842ca3ccef100ce010d1d8f5f6d6cc1915055900) --- Xext/saver.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Xext/saver.c b/Xext/saver.c index f813ba08d..fd6153c31 100644 --- a/Xext/saver.c +++ b/Xext/saver.c @@ -1051,7 +1051,7 @@ ScreenSaverSetAttributes(ClientPtr client) pVlist++; } if (pPriv->attr) - FreeScreenAttr(pPriv->attr); + FreeResource(pPriv->attr->resource, AttrType); pPriv->attr = pAttr; pAttr->resource = FakeClientID(client->index); if (!AddResource(pAttr->resource, AttrType, (void *) pAttr))