Messages in this thread |  | | Date | Mon, 18 Nov 2013 20:16:00 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/3] kill MMF_DUMPABLE and MMF_DUMP_SECURELY |
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On 11/18, Kees Cook wrote: > > On Sat, Nov 16, 2013 at 11:01 AM, Oleg Nesterov <oleg@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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