Re: [Xen-devel] [PATCH v3 1/9] livepatch: Clear .bss when payload is reverted

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.08.16 at 16:29, <konrad.wilk@xxxxxxxxxx> wrote:
> On Mon, Aug 15, 2016 at 04:27:38AM -0600, Jan Beulich wrote:
>> >>> On 14.08.16 at 23:52, <konrad.wilk@xxxxxxxxxx> wrote:
>> > @@ -1034,6 +1047,9 @@ static int revert_payload(struct payload *data)
>> >      list_del_rcu(&data->applied_list);
>> >      unregister_virtual_region(&data->region);
>> >  
>> > +    /* And clear the BSS for subsequent operation. */
>> > +    memset(data->bss, 0, data->bss_size);
>> 
>> Instead of doing it in two places, how about moving this into
>> apply_payload()?
> 
> I was thinking of it too, but then it occurred to me that between the
> 'check' -> 'apply' the BSS is left unitialized. And if we ever crash
> (right as somebody scheduled the livepatch) one could form the opinion
> that it is due to the .bss having garbage. Or more importantly - the
> hooks may not have run, but all its values looked like they have been
> initialized.
> 
> And spend considerable amount of time debugging something which in reality
> is not a problem?
> 
> Perhaps put it in multiple places :-)

Well, you and Ross know. Afaic I'd always do things in just one
place if that's possible.

Jan


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