50 lines
1.7 KiB
Diff
50 lines
1.7 KiB
Diff
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From efca605c45ff51b57f136222b966ce1d610ebc33 Mon Sep 17 00:00:00 2001
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From: Olivier Fourdan <ofourdan@redhat.com>
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Date: Wed, 27 Nov 2024 11:27:05 +0100
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Subject: [PATCH xserver 1/2] Cursor: Refuse to free the root cursor
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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If a cursor reference count drops to 0, the cursor is freed.
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The root cursor however is referenced with a specific global variable,
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and when the root cursor is freed, the global variable may still point
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to freed memory.
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Make sure to prevent the rootCursor from being explicitly freed by a
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client.
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CVE-2025-26594, ZDI-CAN-25544
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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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v2: Explicitly forbid XFreeCursor() on the root cursor (Peter Hutterer
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<peter.hutterer@who-t.net>)
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v3: Return BadCursor instead of BadValue (Michel Dänzer
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<michel@daenzer.net>)
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Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
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Suggested-by: Peter Hutterer <peter.hutterer@who-t.net>
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Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
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---
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dix/dispatch.c | 4 ++++
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1 file changed, 4 insertions(+)
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Index: xwayland-24.1.4/dix/dispatch.c
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===================================================================
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--- xwayland-24.1.4.orig/dix/dispatch.c
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+++ xwayland-24.1.4/dix/dispatch.c
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@@ -3106,6 +3106,10 @@ ProcFreeCursor(ClientPtr client)
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rc = dixLookupResourceByType((void **) &pCursor, stuff->id, RT_CURSOR,
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client, DixDestroyAccess);
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if (rc == Success) {
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+ if (pCursor == rootCursor) {
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+ client->errorValue = stuff->id;
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+ return BadCursor;
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+ }
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FreeResource(stuff->id, RT_NONE);
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return Success;
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}
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