Re: Random arrays on kernel stack..

[Linus Torvalds <torvalds@linux-foundation.org>]

On Fri, Jul 29, 2022 at 10:12 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> That's a good point. Though note that the current WARN_ON is also
> dependent on DEBUG being set.

Sure. And I think that's ok.

> >  (a) that constant should be a bit lower, so that we *can* use a 1kB
> > stack frame warning on 64-bit architectures
>
> That's not so much possible. This needs to do a DFS traversal of the
> trie, which means it can be 128 nodes deep since IPv6 addresses have
> 128 bits.

Ahh. Ok. That at least explains where the constant comes from. That
would be a good thing to have somewhere in that definition of the
value ;)

And I agree that malloc() isn't a great choice.

I don't really worry about the stack frame warning (I just raised it
to the same 2k limit I have on my x86-64 box), so doing that 1k
allocation is fine.

And with that constant 128 explained, I don't think it's wrong to not
even test for overflow. We don't test for things that can't happen.

But *if* you test for it for debug purposes, then at that point I
think you need to just do the "warn and don't corrupt stack".

                     Linus