On Thu, Jul 06, 2017 at 09:29:27PM +0100, Al Viro wrote:
> On Thu, Jul 06, 2017 at 09:18:26PM +0100, Al Viro wrote:
> > On Thu, Jul 06, 2017 at 12:45:36PM -0700, Kees Cook wrote:
> > >
> > > + if (unlikely(!check_copy_size(addr, bytes, false)))
> > > + return false;
> > > + else
> > > + return _copy_from_iter_full(addr, bytes, i);
> > >
> > > Can these be rewritten to avoid the double-negative?
> >
> > Matter of taste - I've no strong preferences here.
> >
> > > + might_fault();
> > >
> > > Should this be might_sleep()? Just from reading the patch it looked
> > > like you were adding might_sleep()s in the other cases.
> >
> > D'oh - shouldn't have written that pull request message before the
> > first cup of coffee... might_sleep() it is, of course.
>
> Hrm... Said that, might_sleep() doesn't check one thing might_fault()
> does - the
> #if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
> if (current->mm)
> might_lock_read(¤t->mm->mmap_sem);
> #endif
> thing. Let me think a bit...
FWIW,
* with iovec-backed, any of those primitives under pagefault_disable()
is seriously wrong. To the point where we probably want to complain when
called that way. That, of course, needs to be checked at the outermost level -
the primitives might do pagefault_disable() internally; that's fine. Outside
caller doing that under pagefault_disable() isn't.
* uaccess_kernel() (== set_fs(KERNEL_DS)) has nothing to do with it.
If anything, we should not do copyin/copyout on iovec-backed ones with that
present.
* telling lockdep that we might end up grabbing ->mm->mmap_sem, OTOH,
is the right thing to do. In addition to might_sleep().
Linus, could you hold that one back until tomorrow? I want to tweak the
last commit in there a bit, but I want to give it a local beating first...
