[Qemu-devel] Re: [PATCH 2/4] Add virtio disk identification support

[john cooper <john.cooper@redhat.com>]

Anthony Liguori wrote:
> On 03/25/2010 12:33 AM, john cooper wrote:
>> Fix bug which truncated serial string to 8 bytes, nul terminate.
>>
>> Signed-off-by: john cooper<john.cooper@redhat.com>
>> ---
>>
>> diff --git a/vl.c b/vl.c
>> index d69250c..b74cbba 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -1162,7 +1162,7 @@ DriveInfo *drive_init(QemuOpts *opts, void *opaque,
>>       dinfo->on_write_error = on_write_error;
>>       dinfo->opts = opts;
>>       if (serial)
>> -        strncpy(dinfo->serial, serial, sizeof(serial));
>> +        strncpy(dinfo->serial, serial, sizeof(dinfo->serial) - 1);
>>    
> 
> You need to explicitly add a null terminator.  Far better to just never
> use strncpy().

As previous this is a case where dinfo->serial[] is defined
as BLOCK_SERIAL_STRLEN + 1 bytes as an internal convenience.
Above the context of the patch here is a:

    dinfo = qemu_mallocz(sizeof(*dinfo));

which assures this will do as intended, namely copy all
potential BLOCK_SERIAL_STRLEN bytes and assure they are
nul terminated should the full length be present.

I didn't conjure up the existing logic but rather am 
trying to peacefully coexist with it.

-john

-- 
john.cooper@redhat.com