linux-kernel - [PATCH v2 2/2] ima: check signature enforcement against cmdline param instead of CONFIG

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Date:   Mon, 23 Oct 2017 14:43:02 -0200
From:   "Bruno E. O. Meneguele" <brdeoliv@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, serge@...lyn.com,
        james.l.morris@...cle.com, dmitry.kasatkin@...il.com,
        zohar@...ux.vnet.ibm.com, rusty@...tcorp.com.au, jeyu@...nel.org
Subject: [PATCH v2 2/2] ima: check signature enforcement against cmdline param instead of CONFIG

When the user requests MODULE_CHECK policy and its kernel is compiled
with CONFIG_MODULE_SIG_FORCE not set, all modules would not load, just
those loaded in initram time. One option the user would have would be
set a kernel cmdline param (module.sig_enforce) to true, but the IMA
module check code doesn't rely on this value, it checks just
CONFIG_MODULE_SIG_FORCE.

This patch solves this problem checking for the exported value of
module.sig_enforce cmdline param intead of CONFIG_MODULE_SIG_FORCE,
which holds the effective value (CONFIG || param).

Signed-off-by: Bruno E. O. Meneguele <brdeoliv@...hat.com>
---
 security/integrity/ima/ima_main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index e4ab8ef8016e..d11a7fcc5c8b 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -356,12 +356,12 @@ void ima_post_path_mknod(struct dentry *dentry)
  */
 int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
 {
+	bool sig_enforce = is_module_sig_enforced();
+
 	if (!file && read_id == READING_MODULE) {
-#ifndef CONFIG_MODULE_SIG_FORCE
-		if ((ima_appraise & IMA_APPRAISE_MODULES) &&
+		if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
 		    (ima_appraise & IMA_APPRAISE_ENFORCE))
 			return -EACCES;	/* INTEGRITY_UNKNOWN */
-#endif
 		return 0;	/* We rely on module signature checking */
 	}
 	return 0;
-- 
2.13.6