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[Qemu-commits] [COMMIT e332340] Fix NULL alarm_timer pointer at exit

From: Anthony Liguori
Subject: [Qemu-commits] [COMMIT e332340] Fix NULL alarm_timer pointer at exit
Date: Wed, 20 May 2009 14:26:58 -0000

From: Jean-Christophe Dubois <address@hidden>

This fixes a SIGSEGV error on qemu exit.

Here is the valgrind output related to this error

==3648== Process terminating with default action of signal 11 (SIGSEGV)
==3648==  Access not within mapped region at address 0x8
==3648==    at 0x40636B: host_alarm_handler (vl.c:1345)
==3648==    by 0x52D807F: (within /lib/libpthread-2.9.so)
==3648==    by 0x5C0A12E: tcsetattr (in /lib/libc-2.9.so)
==3648==    by 0x4DD601: term_exit (qemu-char.c:700)
==3648==    by 0x5B636EC: exit (in /lib/libc-2.9.so)
==3648==    by 0x5B4B5AC: (below main) (in /lib/libc-2.9.so)

This simple fix check for a valid pointer as host_alarm_handler is
also called after alarm_timer is released in the exit path.

Signed-off-by: Jean-Christophe DUBOIS <address@hidden>

diff --git a/vl.c b/vl.c
index 40b1d8b..7034209 100644
--- a/vl.c
+++ b/vl.c
@@ -915,7 +915,7 @@ struct qemu_alarm_timer {
 static inline int alarm_has_dynticks(struct qemu_alarm_timer *t)
-    return t->flags & ALARM_FLAG_DYNTICKS;
+    return t && (t->flags & ALARM_FLAG_DYNTICKS);
 static void qemu_rearm_alarm_timer(struct qemu_alarm_timer *t)
@@ -1349,7 +1349,7 @@ static void host_alarm_handler(int host_signum)
                            qemu_get_clock(rt_clock))) {
-        alarm_timer->flags |= ALARM_FLAG_EXPIRED;
+        if (alarm_timer) alarm_timer->flags |= ALARM_FLAG_EXPIRED;
         if (next_cpu) {

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