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 <address@hidden>
>
> 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 <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

> ---
>  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;