linux-kernel - [PATCH 5/6] notifiers: Use CHECK_DATA

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Date:   Mon,  6 Mar 2017 11:09:45 -0800
From:   Kees Cook <keescook@...omium.org>
To:     kernel-hardening@...ts.openwall.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>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 5/6] notifiers: Use CHECK_DATA_CORRUPTION() on checks

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.

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