On Sun, Apr 7, 2019 at 3:44 PM Thomas Gleixner <t...@linutronix.de> wrote: > > On Sat, 6 Apr 2019, Andy Lutomirski wrote: > > On Fri, Apr 5, 2019 at 8:11 AM Thomas Gleixner <t...@linutronix.de> wrote: > > > > > > From: Andy Lutomirski <l...@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. > > Actually we have: save_stack_trace() >
Like I did here: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/log/?h=WIP.x86/stackguards (Link is bad right now but will hopefully be okay when you read it. I'm still fiddling with the other patches in there -- I'd like to kill kstack_end() entirely.
