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Message-ID: <CAGXu5jJv7ipL+Ang+AWeoUEYapjTH3sKUuSZFKWQWyTSmswwWQ@mail.gmail.com>
Date: Wed, 22 Mar 2017 12:29:24 -0700
From: Kees Cook <keescook@...omium.org>
To: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Kees Cook <keescook@...omium.org>, Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>, Viresh Kumar <viresh.kumar@...aro.org>,
Ingo Molnar <mingo@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
Dmitry Vyukov <dvyukov@...gle.com>, Olof Johansson <olof@...om.net>,
Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 5/6] notifiers: Use CHECK_DATA_CORRUPTION() on checks
On Mon, Mar 6, 2017 at 11:09 AM, Kees Cook <keescook@...omium.org> wrote:
> When performing notifier function pointer sanity checking, allow
> CONFIG_BUG_ON_DATA_CORRUPTION to upgrade from a WARN to a BUG.
> Additionally enables CONFIG_DEBUG_NOTIFIERS when selecting
> CONFIG_BUG_ON_DATA_CORRUPTION.
Any feedback on this change? By default, this retains the existing
WARN behavior...
-Kees
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> kernel/notifier.c | 5 +++--
> lib/Kconfig.debug | 3 ++-
> 2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/notifier.c b/kernel/notifier.c
> index 6196af8a8223..58cc14958d92 100644
> --- a/kernel/notifier.c
> +++ b/kernel/notifier.c
> @@ -84,8 +84,9 @@ static int notifier_call_chain(struct notifier_block **nl,
> next_nb = rcu_dereference_raw(nb->next);
>
> #ifdef CONFIG_DEBUG_NOTIFIERS
> - if (unlikely(!func_ptr_is_kernel_text(nb->notifier_call))) {
> - WARN(1, "Invalid notifier called!");
> + if (CHECK_DATA_CORRUPTION(
> + !func_ptr_is_kernel_text(nb->notifier_call),
> + "Invalid notifier called!")) {
> nb = next_nb;
> continue;
> }
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 42c61cfe7d19..70e9f2c1bb30 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1277,7 +1277,7 @@ config DEBUG_SG
>
> config DEBUG_NOTIFIERS
> bool "Debug notifier call chains"
> - depends on DEBUG_KERNEL
> + depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
> help
> Enable this to turn on sanity checking for notifier call chains.
> This is most useful for kernel developers to make sure that
> @@ -1995,6 +1995,7 @@ config BUG_ON_DATA_CORRUPTION
> bool "Trigger a BUG when data corruption is detected"
> select DEBUG_CREDENTIALS
> select DEBUG_LIST
> + select DEBUG_NOTIFIERS
> select DEBUG_SG
> help
> This option enables several inexpensive data corruption checks.
> --
> 2.7.4
>
--
Kees Cook
Pixel Security
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