Re: [Qemu-devel] [PATCH] fw_cfg_reboot: ensure reboot_time is nonegative

[Markus Armbruster]

Laszlo Ersek <address@hidden> writes:

> On 10/24/18 09:11, Li Qiang wrote:
>> This can avoid setting a negative value to
>> etc/boot-fail-wait.
>> 
>> Signed-off-by: Li Qiang <address@hidden>
>> ---
>>  hw/nvram/fw_cfg.c | 15 ++++++++++-----
>>  1 file changed, 10 insertions(+), 5 deletions(-)
>> 
>> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
>> index f4a52d8..276dcb1 100644
>> --- a/hw/nvram/fw_cfg.c
>> +++ b/hw/nvram/fw_cfg.c
>> @@ -199,12 +199,17 @@ static void fw_cfg_reboot(FWCfgState *s)
>>              reboot_timeout = strtol(p, &p, 10);
>>          }
>>      }
>> -    /* validate the input */
>> -    if (reboot_timeout > 0xffff) {
>> -        error_report("reboot timeout is larger than 65535, force it to 
>> 65535.");
>> -        reboot_timeout = 0xffff;
>> +
>> +    if (reboot_timeout >= 0) {
>> +        /* validate the input */
>> +        if (reboot_timeout > 0xffff) {
>> +            error_report("reboot timeout is larger than 65535,"
>> +                         "force it to 65535.");
>> +            reboot_timeout = 0xffff;
>> +        }
>> +        fw_cfg_add_file(s, "etc/boot-fail-wait",
>> +                        g_memdup(&reboot_timeout, 4), 4);
>>      }
>> -    fw_cfg_add_file(s, "etc/boot-fail-wait", g_memdup(&reboot_timeout, 4), 
>> 4);
>>  }
>>  
>>  static void fw_cfg_write(FWCfgState *s, uint8_t value)
>> 
>
> I don't feel strongly about fixing this issue.
>
> However, if we decide to fix it, we should start with the bare-bones
> strtol() call, visible at the top of the context. I'm not up-to-date on
> what's the best QEMU helper function for this, but I seem to remember it
> checks for trailing garbage, and perhaps even for range. Maybe we should
> even use a different (better) option parsing facility thatn
> qemu_opt_get(). Adding Eric and Markus.

Whenever we qemu_opt_get() a string, then convert it to a number
ourselves, we're doing it wrong.  Can you use qemu_opt_get_number()?

When you have to convert string to integer, use the qemu_strtoX() that
gives you the width and signedness you need.  Or maybe one of the
parse_uint*().

> Also, I would suggest forcing negative values (that were explicitly
> specified) to some sensible positive default, such as 5 seconds or so.
>
> Thanks
> Laszlo