From f6a2ee1c5c20de43e88f69413cc775b700d208c6 Mon Sep 17 00:00:00 2001 From: Peter Hutterer Date: Tue, 20 May 2014 13:48:27 +1000 Subject: [PATCH] mi: don't process events from disabled devices (#77884) Once a device is disabled, it doesn't have a sprite pointer anymore. If an event is still in the queue and processed after DisableDevice finished, a dereference causes a crash. Example backtrace (crash forced by injecting an event at the right time): (EE) 0: /opt/xorg/bin/Xorg (OsSigHandler+0x3c) [0x48d334] (EE) 1: /lib64/libpthread.so.0 (__restore_rt+0x0) [0x37fcc0f74f] (EE) 2: /opt/xorg/bin/Xorg (mieqMoveToNewScreen+0x38) [0x609240] (EE) 3: /opt/xorg/bin/Xorg (mieqProcessDeviceEvent+0xd4) [0x609389] (EE) 4: /opt/xorg/bin/Xorg (mieqProcessInputEvents+0x206) [0x609720] (EE) 5: /opt/xorg/bin/Xorg (ProcessInputEvents+0xd) [0x4aeb58] (EE) 6: /opt/xorg/bin/Xorg (xf86VTSwitch+0x1a6) [0x4af457] (EE) 7: /opt/xorg/bin/Xorg (xf86Wakeup+0x2bf) [0x4af0a7] (EE) 8: /opt/xorg/bin/Xorg (WakeupHandler+0x83) [0x4445cb] (EE) 9: /opt/xorg/bin/Xorg (WaitForSomething+0x3fe) [0x491bf6] (EE) 10: /opt/xorg/bin/Xorg (Dispatch+0x97) [0x435748] (EE) 11: /opt/xorg/bin/Xorg (dix_main+0x61d) [0x4438a9] (EE) 12: /opt/xorg/bin/Xorg (main+0x28) [0x49ba28] (EE) 13: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x37fc821d65] (EE) 14: /opt/xorg/bin/Xorg (_start+0x29) [0x425e69] (EE) 15: ? (?+0x29) [0x29] xf86VTSwitch() calls ProcessInputEvents() before disabling a device, and DisableDevice() calls mieqProcessInputEvents() again when flushing touches and button events. Between that and disabling the device (which causes new events to be refused) there is a window where events may be triggered and enqueued. On the next call to PIE that event is processed on a now defunct device, causing the crash. The simplest fix to this is to discard events from disabled devices. We flush the queue often enough before disabling that when we get here, we really don't care about the events from this device. X.Org Bug 77884 --- mi/mieq.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mi/mieq.c b/mi/mieq.c index 4c07480..188a0b0 100644 --- a/mi/mieq.c +++ b/mi/mieq.c @@ -515,6 +515,10 @@ mieqProcessDeviceEvent(DeviceIntPtr dev, InternalEvent *event, ScreenPtr screen) verify_internal_event(event); + /* refuse events from disabled devices */ + if (!dev->enabled) + return 0; + /* Custom event handler */ handler = miEventQueue.handlers[event->any.type]; -- 1.9.0