linux-kernel - Re: [PATCH 0/4] module: add support for unsafe, tainting parameters

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Message-ID: <87wqac87dq.fsf@rustcorp.com.au>
Date:	Thu, 14 Aug 2014 05:55:05 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jani Nikula <jani.nikula@...el.com>, linux-kernel@...r.kernel.org,
	intel-gfx@...ts.freedesktop.org
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Jon Mason <jon.mason@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>, jani.nikula@...el.com
Subject: Re: [PATCH 0/4] module: add support for unsafe, tainting parameters

Jani Nikula <jani.nikula@...el.com> writes:
> This is a generic version of Daniel's patch [1] letting us have unsafe
> module parameters (experimental, debugging, testing, etc.) that taint
> the kernel when set. Quoting Daniel,

OK, I think the idea is fine, but we'll probably only want this for
a few types (eg. int and bool).  So for the moment I prefer a more
naive approach.

Does this work for you?

Subject: module: add taint_int type

An int parameter which taints the kernel if set; i915 at least wants this.

Based-on-patches-by: Daniel Vetter <daniel.vetter@...ll.ch>
Based-on-patches-by: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 494f99e852da..99ba68206ba4 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -408,6 +408,10 @@ extern int param_set_bint(const char *val, const struct kernel_param *kp);
 #define param_get_bint param_get_int
 #define param_check_bint param_check_int
 
+/* An int, which taints the kernel if set. */
+extern struct kernel_param_ops param_ops_taint_int;
+#define param_check_taint_int param_check_int
+
 /**
  * module_param_array - a parameter which is an array of some type
  * @name: the name of the array variable
diff --git a/kernel/params.c b/kernel/params.c
index 34f527023794..3128218158cf 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -375,6 +375,20 @@ struct kernel_param_ops param_ops_bint = {
 };
 EXPORT_SYMBOL(param_ops_bint);
 
+static int param_set_taint_int(const char *val, const struct kernel_param *kp)
+{
+	pr_warn("Setting dangerous option %s - tainting kernel\n", kp->name);
+	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
+
+	return param_set_int(val, kp);
+}
+
+struct kernel_param_ops param_ops_taint_int = {
+	.set = param_set_taint_int,
+	.get = param_get_int,
+};
+EXPORT_SYMBOL(param_ops_taint_int);
+
 /* We break the rule and mangle the string. */
 static int param_array(const char *name,
 		       const char *val,
--
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