On Tue, Jul 31, 2012 at 12:21:58PM +0200, richard -rw- weinberger wrote:
> On Tue, Jul 31, 2012 at 12:16 PM, Cyrill Gorcunov <gorcunov@xxxxxxxxxx> wrote:
> > On Tue, Jul 31, 2012 at 12:08:22PM +0200, richard -rw- weinberger wrote:
> >> On Tue, Jul 31, 2012 at 11:54 AM, Pavel Emelyanov <xemul@xxxxxxxxxxxxx> wrote:
> >> >> Yeah, but I fear it's not that easy.
> >> >> We'd have to change crtools to work without ptrace().
> >> >
> >> > Well, this is hard. Using ptrace saved us from having many special-purpose
> >> > APIs for dumping various stuff (there will be an article about it). Thus I
> >> > don't know which way is simpler -- stop using ptrace or teach ptrece to allow
> >> > several tracers to attach to one task %)
> >>
> >> Allowing multiple tracers in a safe way is IMHO even more harder.
> >>
> >> BTW: While reading prctl_set_mm() I noticed two things.
> >> 1. Why isn't the return value of find_vma() verified?
> >
> > prctl_set_mm
> > vma = find_vma(mm, addr);
> > ...
> > if (!vma) {
> > error = -EFAULT;
> > goto out;
> > }
> >
> > these values are used in procfs statistics only. So I don't get
> > which verify you mean here.
>
> If I do PR_SET_MM_START_BRK the if(!vma) will never be executed because
> there a break in case PR_SET_MM_START_BRK.
Yes, and this is done by purpose, since we need to setup _completely_
new memory map on restore procedure.
There is a minimal check for value being sane
if (addr >= TASK_SIZE || addr < mmap_min_addr)
return -EINVAL;
and the address belongs to mm::start_data|end_data area. But sure,
better to add checks that at least code/data areas do exist, otherwise
the proc output will not reflect the real state of memory maps.
Cyrill
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