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