From: Daniel Axtens <dja@axtens.net>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, kasan-dev@googlegroups.com
Cc: dvyukov@google.com, christophe.leroy@c-s.fr,
Daniel Axtens <dja@axtens.net>
Subject: [PATCH v4 0/2] Fix some incompatibilites between KASAN and FORTIFY_SOURCE
Date: Sat, 25 Apr 2020 00:55:19 +1000 [thread overview]
Message-ID: <20200424145521.8203-1-dja@axtens.net> (raw)
3 KASAN self-tests fail on a kernel with both KASAN and FORTIFY_SOURCE:
memchr, memcmp and strlen. I have observed this on x86 and powerpc.
When FORTIFY_SOURCE is on, a number of functions are replaced with
fortified versions, which attempt to check the sizes of the
operands. However, these functions often directly invoke __builtin_foo()
once they have performed the fortify check.
This breaks things in 2 ways:
- the three function calls are technically dead code, and can be
eliminated. When __builtin_ versions are used, the compiler can detect
this.
- Using __builtins may bypass KASAN checks if the compiler decides to
inline it's own implementation as sequence of instructions, rather than
emit a function call that goes out to a KASAN-instrumented
implementation.
The patches address each reason in turn.
v4: Drop patch 3, it turns out I created that issue in patch 1!
Include David's Tested-by.
v3: resend with Reviewed-bys, hopefully for inclusion in 5.8.
v2: - some cleanups, don't mess with arch code as I missed some wrinkles.
- add stack array init (patch 3)
Daniel Axtens (2):
kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE
string.h: fix incompatibility between FORTIFY_SOURCE and KASAN
include/linux/string.h | 60 +++++++++++++++++++++++++++++++++---------
lib/test_kasan.c | 29 +++++++++++++-------
2 files changed, 67 insertions(+), 22 deletions(-)
--
2.20.1
next reply other threads:[~2020-04-24 14:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-24 14:55 Daniel Axtens [this message]
2020-04-24 14:55 ` [PATCH v4 1/2] kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE Daniel Axtens
2020-04-24 14:55 ` [PATCH v4 2/2] string.h: fix incompatibility between FORTIFY_SOURCE and KASAN Daniel Axtens
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200424145521.8203-1-dja@axtens.net \
--to=dja@axtens.net \
--cc=akpm@linux-foundation.org \
--cc=christophe.leroy@c-s.fr \
--cc=dvyukov@google.com \
--cc=kasan-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).