On Mon, May 14, 2018 at 04:53:12PM +0300, Alexander Popov wrote:

On 14.05.2018 13:06, Mark Rutland wrote:

quoted

I think it is reasonable to panic() here even with CONFIG_VMAP_STACK
selected.

It's too tough for CONFIG_VMAP_STACK on x86 - the system can proceed to live.
Anyway, the check_alloca() code will not be shared between x86 and arm64, I've
described the reasons in this thread. So I can have BUG() for CONFIG_VMAP_STACK
on x86 and Laura can consistently use panic() on arm64.

If we need arch-specific implementations anyway, then that's fine by me.

quoted

quoted

So we should not do it in check_alloca() as well, just use BUG() and
hope for the best.

Regardless of whether we BUG() or panic(), we're hoping for the best.

Consistently using panic() here will keep things simpler, so any failure
reported will be easier to reason about, and easier to debug.

Let me keep BUG() for !CONFIG_SCHED_STACK_END_CHECK. I beware of using panic()
by default, let distro/user decide this. I remember very well how I was shouted
at, when this one was merged:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ce6fa91b93630396ca220c33dd38ffc62686d499

Sure; my comments needn't hold up your patches.

Thanks,
Mark.