Re: [Qemu-devel] [PATCH] multiboot: copy the cmdline verbatim

[Paolo Bonzini]

On 14/12/2016 18:00, Eduardo Habkost wrote:
> On Wed, Dec 14, 2016 at 05:55:07PM +0100, Paolo Bonzini wrote:
>>
>>
>> On 14/12/2016 17:19, Vlad Lungu wrote:
>>> get_opt_value() truncates the value at the first comma.
>>> Use memcpy() instead.
>>
>> Looks good since get_opt_value is already used by the caller.  Have you
>> tested this with multiple initrd modules too?
> 
> get_opt_value() is used by the caller, but with NULL buf
> argument. This means the caller doesn't handle ",," escaping.
> (See my reply to the previous submission of this patch)

Hmm, wait.  When NULL is passed, ",," escaping is handled correctly in
that next_initrd points to the next lone comma.  The lone comma is
replaced with a '\0' by the caller.

So you need to use get_opt_value again in mb_add_cmdline to do the
unescaping, because mb_add_cmdline only receives double commas.

This was actually my first reaction to the patch, and it was correct.
Then I overthought it. :)

So the patch is wrong.

Paolo

> However this only means the caller is buggy, not
> mb_add_cmdline(). So the change still looks good to me.
> 
>>
>> Paolo
>>
>>> Signed-off-by: Vlad Lungu <address@hidden>
>>> ---
>>>  hw/i386/multiboot.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
>>> index 387caa6..b4495ad 100644
>>> --- a/hw/i386/multiboot.c
>>> +++ b/hw/i386/multiboot.c
>>> @@ -109,7 +109,7 @@ static uint32_t mb_add_cmdline(MultibootState *s, const 
>>> char *cmdline)
>>>      hwaddr p = s->offset_cmdlines;
>>>      char *b = (char *)s->mb_buf + p;
>>>  
>>> -    get_opt_value(b, strlen(cmdline) + 1, cmdline);
>>> +    memcpy(b, cmdline, strlen(cmdline) + 1);
>>>      s->offset_cmdlines += strlen(b) + 1;
>>>      return s->mb_buf_phys + p;
>>>  }
>>>
>