Re: [Qemu-devel] [PATCH] hw/9pfs/virtio-9p-local.c: use snprintf() instead of sprintf()

[Chen Gang]

On 02/03/2014 06:39 PM, Chen Gang wrote:
> On 02/03/2014 06:34 PM, Daniel P. Berrange wrote:
>> On Mon, Feb 03, 2014 at 06:00:42PM +0800, Chen Gang wrote:
>>> We can not assume "'path' + 'ctx->fs_root'" must be less than MAX_PATH,
>>> so need use snprintf() instead of sprintf().
>>>
>>> And also recommend to use ARRAY_SIZE instead of hard code macro for an
>>> array size in snprintf().
>>
>> In the event that there is overflow this will cause the data to be
>> truncated, potentially causing QEMU to access the wrong file on the
>> host. Both snprintf and sprintf are really bad because of their
>> use of fixed buffers. Better to change it to g_strdup_printf which
>> dynamically allocates buffers.
>>

After check the details, I guess we can not change to g_strdup_printf or
others (e.g. v9fs_string_*).

v9fs need use "mkdir, remove ..." which have MAX_PATH limitation. So if
the combined path is longer than MAX_PATH, before it passes to "mkdir,
remove ...", it has to be truncated just like what rpath() has done.

So for me, we have to still use snprintf() instead of sprintf(), but
really need provide the related comments under each snprintf().

> 
> That sounds reasonable to me, I will send patch v2 for it.
> 
> 
> Thanks.
> 

Thanks.
-- 
Chen Gang

Open, share and attitude like air, water and life which God blessed