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From 6b59bdddf30dde413c4e0391cf84f3b94d4b4e31 Mon Sep 17 00:00:00 2001
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From: Peter Hutterer <peter.hutterer@who-t.net>
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Date: Tue, 29 Nov 2022 14:53:07 +1000
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Subject: [PATCH xserver 5/7] Xext: free the screen saver resource when
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replacing it
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This fixes a use-after-free bug:
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When a client first calls ScreenSaverSetAttributes(), a struct
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ScreenSaverAttrRec is allocated and added to the client's
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resources.
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When the same client calls ScreenSaverSetAttributes() again, a new
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struct ScreenSaverAttrRec is allocated, replacing the old struct. The
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old struct was freed but not removed from the clients resources.
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Later, when the client is destroyed the resource system invokes
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ScreenSaverFreeAttr and attempts to clean up the already freed struct.
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Fix this by letting the resource system free the old attrs instead.
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CVE-2022-46343, ZDI-CAN 19404
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This vulnerability was discovered by:
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Jan-Niklas Sohn working with Trend Micro Zero Day Initiative
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Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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Acked-by: Olivier Fourdan <ofourdan@redhat.com>
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---
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Xext/saver.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/Xext/saver.c b/Xext/saver.c
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index f813ba08d1..fd6153c313 100644
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--- a/Xext/saver.c
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+++ b/Xext/saver.c
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@@ -1051,7 +1051,7 @@ ScreenSaverSetAttributes(ClientPtr client)
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pVlist++;
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}
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if (pPriv->attr)
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- FreeScreenAttr(pPriv->attr);
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+ FreeResource(pPriv->attr->resource, AttrType);
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pPriv->attr = pAttr;
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pAttr->resource = FakeClientID(client->index);
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if (!AddResource(pAttr->resource, AttrType, (void *) pAttr))
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--
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2.38.1
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