timers_state.icount_time_shift must be in [0,63] to avoid undefined
behavior when shifting by it, e.g. in cpu_icount_to_ns().
icount_adjust() clamps it to [0,MAX_ICOUNT_SHIFT], with
MAX_ICOUNT_SHIFT = 10.  configure_icount() doesn't.  Fix that.

Fixes: a8bfac37085c3372366d722f131a7e18d664ee4d
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 cpus.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/cpus.c b/cpus.c
index 1b542b37f9..5670c96bcf 100644
--- a/cpus.c
+++ b/cpus.c
@@ -25,6 +25,7 @@
 #include "qemu/osdep.h"
 #include "qemu-common.h"
 #include "qemu/config-file.h"
+#include "qemu/cutils.h"
 #include "migration/vmstate.h"
 #include "monitor/monitor.h"
 #include "qapi/error.h"
@@ -801,7 +802,6 @@ void configure_icount(QemuOpts *opts, Error **errp)
     bool sleep = qemu_opt_get_bool(opts, "sleep", true);
     bool align = qemu_opt_get_bool(opts, "align", false);
     long time_shift = -1;
-    char *rem_str = NULL;
 
     if (!option && qemu_opt_get(opts, "align")) {
         error_setg(errp, "Please specify shift option when using align");
@@ -814,9 +814,8 @@ void configure_icount(QemuOpts *opts, Error **errp)
     }
 
     if (strcmp(option, "auto") != 0) {
-        errno = 0;
-        time_shift = strtol(option, &rem_str, 0);
-        if (errno != 0 || *rem_str != '\0' || !strlen(option)) {
+        if (qemu_strtol(option, NULL, 0, &time_shift) < 0
+            || time_shift < 0 || time_shift > MAX_ICOUNT_SHIFT) {
             error_setg(errp, "icount: Invalid shift value");
             return;
         }
-- 
2.21.1