Re: [PATCH 5/5] x86/traps: avoid KMSAN bugs originating from handle_bug()

Peter Zijlstra
2022-11-02T12:51:26Z

On Wed, Nov 02, 2022 at 12:06:11PM +0100, Alexander Potapenko wrote:
> There is a case in exc_invalid_op handler that is executed outside the
> irqentry_enter()/irqentry_exit() region when an UD2 instruction is used
> to encode a call to __warn().
>
> In that case the `struct pt_regs` passed to the interrupt handler is
> never unpoisoned by KMSAN (this is normally done in irqentry_enter()),
> which leads to false positives inside handle_bug().
>
> Use kmsan_unpoison_entry_regs() to explicitly unpoison those registers
> before using them.

As does poke_int3_handler(); does that need fixing up too? OTOH look
*very very* carefully at the contraints there.