Re: [Xen-devel] [PATCH] tapdisk2: initialize 'name' parameter of BLKTAP2_IOCTL_CREATE_DEVICE

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.03.12 at 16:53, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> Jan Beulich writes ("[Xen-devel] [PATCH] tapdisk2: initialize 'name' 
> parameter 
> of BLKTAP2_IOCTL_CREATE_DEVICE"):
>> This keeps the kernel driver from printing garbage.
> ...
>> +    strncpy(params.name, vbd->name, BLKTAP2_MAX_MESSAGE_LEN);
> 
> I don't think this is right.  As the FM for strncpy puts it:
> 
>  |        Warning: If there is no null byte among the first n bytes
>  | of src, the string placed in dest will not be null-terminated.

That's actually expected here - the kernel code needs to be careful
about no trailing NUL anyway.

> An easy fix would be to memset params to 0 first.

That would not help at all - if src is longer than available space, then
there still wouldn't be a NUL in the end. On would additionally have to
subtract 1 from the size argument. But as said, all that is unnecessary.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel