linux-hardening - [PATCH 0/3] wchan: Fix ORC support and leaky fallback

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Date:   Thu, 23 Sep 2021 23:20:03 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Helge Deller <deller@....de>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Vito Caputo <vcaputo@...garu.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jann Horn <jannh@...gle.com>, "Tobin C. Harding" <me@...in.cc>,
        Tycho Andersen <tycho@...ho.pizza>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Mark Rutland <mark.rutland@....com>,
        Jens Axboe <axboe@...nel.dk>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Stefan Metzmacher <metze@...ba.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Michal Hocko <mhocko@...e.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Ohhoon Kwon <ohoono.kwon@...sung.com>,
        YiFei Zhu <yifeifz2@...inois.edu>,
        kernel test robot <oliver.sang@...el.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux-hardening@...r.kernel.org, x86@...nel.org,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH 0/3] wchan: Fix ORC support and leaky fallback

Hi,

This attempts to solve the issues from the discussion
here[1]. Specifically:

1) wchan has been broken under ORC, seen as a failure to stack walk
   resulting in _usually_ a 0 value, since ee9f8fce9964 (v4.14).

2) wchan leaking raw addresses since 152c432b128c (v5.12).

Based on what I can see in the stack walking code, the fix should be
safe. Jann may have more thoughts, but from what I can see, the walker
pins the stack, decodes only a single step, etc.

I'd like Josh's review of Qi Zheng's patch, though. :)

It's also not clear to me what impact this had on kernel/sched/fair.c:
it would have also been seeing 0s, so this may be fixing a bug there too.

Thanks!

-Kees

[1] https://lore.kernel.org/lkml/20210924054647.v6x6risoa4jhuu6s@shells.gnugeneration.com/

Kees Cook (2):
  Revert "proc/wchan: use printk format instead of lookup_symbol_name()"
  leaking_addresses: Always print a trailing newline

Qi Zheng (1):
  x86: Fix get_wchan() to support the ORC unwinder

 arch/x86/kernel/process.c    | 51 +++---------------------------------
 fs/proc/base.c               | 19 ++++++++------
 scripts/leaking_addresses.pl |  3 ++-
 3 files changed, 16 insertions(+), 57 deletions(-)

-- 
2.30.2