On Fri, Apr 5, 2019 at 8:11 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> From: Andy Lutomirski <luto@kernel.org>
>
> The IRQ stack lives in percpu space, so an IRQ handler that overflows it
> will overwrite other data structures.
>
> Use vmap() to remap the IRQ stack so that it will have the usual guard
> pages that vmap/vmalloc allocations have. With this the kernel will panic
> immediately on an IRQ stack overflow.

The 0day bot noticed that this dies with DEBUG_PAGEALLOC on.  This is
because the store_stackinfo() function is utter garbage and this patch
correctly detects just how broken it is.  The attached patch "fixes"
it.  (It also contains a reliability improvement that should probably
get folded in, but is otherwise unrelated.)

A real fix would remove the generic kstack_end() function entirely
along with __HAVE_ARCH_KSTACK_END and would optionally replace
store_stackinfo() with something useful.  Josh, do we have a generic
API to do a little stack walk like this?  Otherwise, I don't think it
would be the end of the world to just remove the offending code.

--Andy