Re: [Qemu-devel] [PATCH 1/2] monitor.c: make mon_get_cpu return NULL when there is no CPU

[Philippe Mathieu-Daudé]

On 02/17/2017 05:27 AM, Ziyue Yang wrote:

From: Ziyue Yang <yzyliv...@hotmail.com>

Currently mon_get_cpu always dereferences first_cpu without checking
whether it's a valid pointer. This commit adds check before dereferencing,
and reports "No CPU" info if there isn't any CPU then returns NULL.

Signed-off-by: Ziyue Yang <skiver.cloud....@gmail.com>

Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>

---
 monitor.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/monitor.c b/monitor.c
index 3cd72a9bab..6b25cf7a2b 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1026,6 +1026,10 @@ int monitor_set_cpu(int cpu_index)
 CPUState *mon_get_cpu(void)
 {
     if (!cur_mon->mon_cpu) {
+        if (!first_cpu) {
+            monitor_printf(cur_mon, "No CPU available on this machine\n");
+            return NULL;
+        }
         monitor_set_cpu(first_cpu->cpu_index);
     }
     cpu_synchronize_state(cur_mon->mon_cpu);
@@ -2495,11 +2499,11 @@ static int default_fmt_size = 4;
 static int is_valid_option(const char *c, const char *typestr)
 {
     char option[3];
-
+
     option[0] = '-';
     option[1] = *c;
     option[2] = '\0';
-
+
     typestr = strstr(typestr, option);
     return (typestr != NULL);
 }
@@ -2864,7 +2868,7 @@ static QDict *monitor_parse_arguments(Monitor *mon,
                     p++;
                     if(c != *p) {
                         if(!is_valid_option(p, typestr)) {
-
+
                             monitor_printf(mon, "%s: unsupported option -%c\n",
                                            cmd->name, *p);
                             goto fail;