[PATCH -fixes v3 0/6] Fixes KASAN and other along the way

[Alexandre Ghiti]

On Fri, Feb 25, 2022 at 2:06 PM Marco Elver <elver at google.com> wrote:
>
> On Fri, 25 Feb 2022 at 13:40, Alexandre Ghiti
> <alexandre.ghiti at canonical.com> wrote:
> >
> > As reported by Aleksandr, syzbot riscv is broken since commit
> > 54c5639d8f50 ("riscv: Fix asan-stack clang build"). This commit actually
> > breaks KASAN_INLINE which is not fixed in this series, that will come later
> > when found.
> >
> > Nevertheless, this series fixes small things that made the syzbot
> > configuration + KASAN_OUTLINE fail to boot.
> >
> > Note that even though the config at [1] boots fine with this series, I
> > was not able to boot the small config at [2] which fails because
> > kasan_poison receives a really weird address 0x4075706301000000 (maybe a
> > kasan person could provide some hint about what happens below in
> > do_ctors -> __asan_register_globals):
>
> asan_register_globals is responsible for poisoning redzones around
> globals. As hinted by 'do_ctors', it calls constructors, and in this
> case a compiler-generated constructor that calls
> __asan_register_globals with metadata generated by the compiler. That
> metadata contains information about global variables. Note, these
> constructors are called on initial boot, but also every time a kernel
> module (that has globals) is loaded.
>
> It may also be a toolchain issue, but it's hard to say. If you're
> using GCC to test, try Clang (11 or later), and vice-versa.

I tried 3 different gcc toolchains already, but that did not fix the
issue. The only thing that worked was setting asan-globals=0 in
scripts/Makefile.kasan, but ok, that's not a fix.
I tried to bisect this issue but our kasan implementation has been
broken quite a few times, so it failed.

I keep digging!

Thanks for the tips,

Alex