On 11/18, Kees Cook wrote:
>
> On Sat, Nov 16, 2013 at 11:01 AM, Oleg Nesterov <o...@redhat.com> wrote:
> > @@ -1629,24 +1628,13 @@ void set_dumpable(struct mm_struct *mm, int value)
> >
> > do {
> > old = ACCESS_ONCE(mm->flags);
> > - new = old & ~MMF_DUMPABLE_MASK;
> > -
> > - switch (value) {
> > - case SUID_DUMP_ROOT:
> > - new |= (1 << MMF_DUMP_SECURELY);
> > - case SUID_DUMP_USER:
> > - new |= (1<< MMF_DUMPABLE);
> > - }
> > -
> > + new = (old & ~MMF_DUMPABLE_MASK) | value;
>
> Just to make this safe against insane callers, perhaps mask the value as well?
Well yes, before this patch set_dumpable() silently ignored the wrong
value, perhaps you are right but see below.
> new = (old & ~MMF_DUMPABLE_MASK) | (value & MMF_DUMPABLE_MASK);
^^^^^^^^^^^^^^^^^^^^^^^^^^
this doesn't really help, with this patch "mm->flags & MMF_DUMPABLE_MASK"
has a room for yet another SUID_DUMP == 4 we do not have yet.
And I don't really like the "silently ignore" logic, so perhaps
if (WARN_ON(value > SUID_DUMP_ROOT))
return;
at the start makes more sense?
Or perhaps we do not really need the additional check? suid_dumpable
is always sane, other callers can't use the wrong value.
But I am fine either way, please tell me what do you prefer.
Oleg.
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