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From 1801fe0ac3926882d47d7e1ad6c0518a2cdffd41 Mon Sep 17 00:00:00 2001
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From: Povilas Kanapickas <povilas@radix.lt>
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Date: Sun, 19 Dec 2021 18:11:07 +0200
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Subject: [PATCH] dix: Fix use after free in input device shutdown
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This fixes access to freed heap memory via dev->master. E.g. when
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running BarrierNotify.ReceivesNotifyEvents/7 test from
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xorg-integration-tests:
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==24736==ERROR: AddressSanitizer: heap-use-after-free on address
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0x619000065020 at pc 0x55c450e2b9cf bp 0x7fffc532fd20 sp 0x7fffc532fd10
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READ of size 4 at 0x619000065020 thread T0
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#0 0x55c450e2b9ce in GetMaster ../../../dix/devices.c:2722
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#1 0x55c450e9d035 in IsFloating ../../../dix/events.c:346
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#2 0x55c4513209c6 in GetDeviceUse ../../../Xi/xiquerydevice.c:525
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../../../Xi/xichangehierarchy.c:95
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#4 0x55c450e3455c in RemoveDevice ../../../dix/devices.c:1204
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../../../hw/xfree86/common/xf86Xinput.c:1142
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#6 0x55c450e17b04 in CloseDeviceList ../../../dix/devices.c:1038
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#7 0x55c450e1de85 in CloseDownDevices ../../../dix/devices.c:1068
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#8 0x55c450e837ef in dix_main ../../../dix/main.c:302
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#9 0x55c4517a8d93 in main ../../../dix/stubmain.c:34
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(/lib/x86_64-linux-gnu/libc.so.6+0x28564)
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#11 0x55c450d0113d in _start (/usr/lib/xorg/Xorg+0x117713d)
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0x619000065020 is located 160 bytes inside of 912-byte region
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[0x619000064f80,0x619000065310)
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freed by thread T0 here:
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(/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10d7cf)
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#1 0x55c450e19f1c in CloseDevice ../../../dix/devices.c:1014
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#2 0x55c450e343a4 in RemoveDevice ../../../dix/devices.c:1186
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../../../hw/xfree86/common/xf86Xinput.c:1142
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#4 0x55c450e17b04 in CloseDeviceList ../../../dix/devices.c:1038
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#5 0x55c450e1de85 in CloseDownDevices ../../../dix/devices.c:1068
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#6 0x55c450e837ef in dix_main ../../../dix/main.c:302
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#7 0x55c4517a8d93 in main ../../../dix/stubmain.c:34
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(/lib/x86_64-linux-gnu/libc.so.6+0x28564)
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previously allocated by thread T0 here:
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(/usr/lib/x86_64-linux-gnu/libasan.so.5+0x10ddc6)
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#1 0x55c450e1c57b in AddInputDevice ../../../dix/devices.c:259
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#2 0x55c450e34840 in AllocDevicePair ../../../dix/devices.c:2755
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#3 0x55c45130318f in add_master ../../../Xi/xichangehierarchy.c:152
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../../../Xi/xichangehierarchy.c:465
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#5 0x55c4512cb9f5 in ProcIDispatch ../../../Xi/extinit.c:390
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#6 0x55c450e6a92b in Dispatch ../../../dix/dispatch.c:551
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#7 0x55c450e834b7 in dix_main ../../../dix/main.c:272
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#8 0x55c4517a8d93 in main ../../../dix/stubmain.c:34
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(/lib/x86_64-linux-gnu/libc.so.6+0x28564)
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The problem is caused by dev->master being not reset when disabling the
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device, which then causes dangling pointer when the master device itself
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is being deleted when exiting whole server.
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Note that RecalculateMasterButtons() requires dev->master to be still
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valid, so we can reset it only at the end of function.
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Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
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---
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dix/devices.c | 1 +
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1 file changed, 1 insertion(+)
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diff --git a/dix/devices.c b/dix/devices.c
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index e62c34c55..5f9ce1678 100644
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--- a/dix/devices.c
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+++ b/dix/devices.c
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@@ -520,6 +520,7 @@ DisableDevice(DeviceIntPtr dev, BOOL sendevent)
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}
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RecalculateMasterButtons(dev);
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+ dev->master = NULL;
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return TRUE;
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}
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--
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2.43.0
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