Re: [Xen-devel] [PATCH 10/16] libelf: check all pointer accesses

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Thu, Jun 6, 2013 at 3:51 PM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:
>> I realize that technically you've said "dest_size=0 -> dest_base is
>> also invalid", but it never hurts to have a little extra safety.
>
> If there is any code which accesses elf->dest_base[] without checking
> elf->dest_size then that code is already a problem.
>
> Making the change you propose would raise questions about whether (eg)
> some other code somewhere might think dest_base==0 means something
> special.  (I don't think it does, but it's an argument against
> changing things.)

Yes, of course there is a problem; what I was suggesting was,
supposing there were such a problem, which would be most likely to
show it up in a helpful way -- setting dest_base to 0, or leaving it
to what is (at the moment) a valid address?

We could also, I suppose, do "dest_base+=dest_size" before setting
dest_size to 0.  Then dest_base in theory shouldn't be a valid address
either.

 -George

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