linux-kernel - [PATCH v2] init, allow blacklisting of module

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Date:	Thu, 16 Jun 2016 20:46:27 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Prarit Bhargava <prarit@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Yang Shi <yang.shi@...aro.org>, Ingo Molnar <mingo@...nel.org>,
	Mel Gorman <mgorman@...e.de>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Kees Cook <keescook@...omium.org>,
	Yaowei Bai <baiyaowei@...s.chinamobile.com>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: [PATCH v2] init, allow blacklisting of module_init functions

sprint_symbol_no_offset() returns the string "function_name [module_name]"
where [module_name] is not printed for built in kernel functions.  This
means that the blacklisting code will fail when comparing module function
names with the extended string.  This patch adds the functionality to
block a module's module_init() function by finding the space in the string
and truncating the comparison to that length.

[v2]: linux@...musvillemoes.dk, switch to strreplace()

Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Yang Shi <yang.shi@...aro.org>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Kees Cook <keescook@...omium.org>
Cc: Yaowei Bai <baiyaowei@...s.chinamobile.com>
Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
---
 init/main.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/init/main.c b/init/main.c
index 4c17fda5c2ff..e8fb1b537d08 100644
--- a/init/main.c
+++ b/init/main.c
@@ -713,6 +713,11 @@ static bool __init_or_module initcall_blacklisted(initcall_t fn)
 		return false;
 
 	sprint_symbol_no_offset(fn_name, (unsigned long)fn);
+	/*
+	 * fn will be "function_name [module_name]" where [module_name] is not
+	 * displayed for built-in init functions.  Strip off the [module_name].
+	 */
+	strreplace(fn_name, ' ', '\0');
 
 	list_for_each_entry(entry, &blacklisted_initcalls, next) {
 		if (!strcmp(fn_name, entry->buf)) {
-- 
1.7.9.3