Re: [Qemu-devel] [PATCH 2/2] xen: Don't peek behind the BlockDriverState abstraction

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> On 6 June 2012 13:55, Markus Armbruster <address@hidden> wrote:
>> Peter Maydell <address@hidden> writes:
>>
>>> On 5 June 2012 13:51, Markus Armbruster <address@hidden> wrote:
>>>> @@ -554,6 +553,7 @@ static int blk_init(struct XenDevice *xendev)
>>>>  {
>>>>     struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, 
>>>> xendev);
>>>>     int index, qflags, info = 0;
>>>> +    char fmt_name[128];
>>>
>>> Fixed length array with a hardcoded magic number size ?
>>> If the block layer guarantees that format names are going to be
>>> less than 128 bytes it ought to provide a suitable #define for
>>> people to set array sizes to...
>>
>> Maybe it should, but it doesn't.  Does it really matter in this
>> particular case?  If somebody insists on giving his driver a name longer
>> than 127 characters, we'll silently log it truncated, that's all.
>
> I think it matters in the general case, yours is just the first
> usage of this API which has caught my attention. We should fix
> the API before adding more uses of it (at the moment it seems to
> be only used in two places).

What kind of fix do you have in mind?

> Alternatively, we could have the function return a const char* rather
> than taking a buffer to be filled in.

Trades the theoretical string truncation problem for a theoretical
dangling pointer problem.