linux-kernel - [PATCH v3 0/3] Actually fix freelist pointer vs redzoning

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Message-Id: <20201015033712.1491731-1-keescook@chromium.org>
Date:   Wed, 14 Oct 2020 20:37:09 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Christoph Lameter <cl@...ux.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Waiman Long <longman@...hat.com>,
        Marco Elver <elver@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Roman Gushchin <guro@...com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v3 0/3] Actually fix freelist pointer vs redzoning

v3:
- fix commit messages to properly reflect the direction of the overwrite
- justify the less-than-word-size patch better
- add Acks
- move some Fixes up into the commit log as just references
v2: https://lore.kernel.org/lkml/20201009195411.4018141-1-keescook@chromium.org
v1: https://lore.kernel.org/lkml/20201008233443.3335464-1-keescook@chromium.org

This fixes redzoning vs the freelist pointer (both for middle-position
and very small caches). Both are "theoretical" fixes, in that I see no
evidence of such small-sized caches actually be used in the kernel, but
that's no reason to let the bugs continue to exist. :)

Note on patch 2: Christopher NAKed it, but I actually think this is a
reasonable thing to add -- the "too small" check is only made when built
with CONFIG_DEBUG_VM, so it *is* actually possible for someone to trip
over this directly, even if it would never make it into a released
kernel. I see no reason to just leave this foot-gun in place, though, so
we might as well just fix it too. (Which seems to be what Longman was
similarly supporting, IIUC.)

Anyway, if patch 2 stays NAKed, that's fine. It's entirely separable,
and the other 2 can land. :)

Thanks!

-Kees

Kees Cook (3):
  mm/slub: Clarify verification reporting
  mm/slub: Fix redzoning for small allocations
  mm/slub: Actually fix freelist pointer vs redzoning

 Documentation/vm/slub.rst | 10 +++++-----
 mm/slub.c                 | 36 +++++++++++++++---------------------
 2 files changed, 20 insertions(+), 26 deletions(-)

-- 
2.25.1