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Message-Id: <93a44c8854b914fb9558fd37b7c4c9ee6051c20c.1549927666.git.igor.stoppa@huawei.com>
Date: Tue, 12 Feb 2019 01:27:49 +0200
From: Igor Stoppa <igor.stoppa@...il.com>
To:
Cc: Igor Stoppa <igor.stoppa@...wei.com>,
Andy Lutomirski <luto@...capital.net>,
Nadav Amit <nadav.amit@...il.com>,
Matthew Wilcox <willy@...radead.org>,
Peter Zijlstra <peterz@...radead.org>,
Kees Cook <keescook@...omium.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Mimi Zohar <zohar@...ux.vnet.ibm.com>,
Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
Ahmed Soliman <ahmedsoliman@...a.vt.edu>,
linux-integrity@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH v4 12/12] IMA: turn ima_policy_flags into __wr_after_init
The policy flags could be targeted by an attacker aiming at disabling IMA,
so that there would be no trace of a file system modification in the
measurement list.
Since the flags can be altered at runtime, it is not possible to make
them become fully read-only, for example with __ro_after_init.
__wr_after_init can still provide some protection, at least against
simple memory overwrite attacks
Signed-off-by: Igor Stoppa <igor.stoppa@...wei.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Nadav Amit <nadav.amit@...il.com>
CC: Matthew Wilcox <willy@...radead.org>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Kees Cook <keescook@...omium.org>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: Mimi Zohar <zohar@...ux.vnet.ibm.com>
CC: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
CC: Ahmed Soliman <ahmedsoliman@...a.vt.edu>
CC: linux-integrity@...r.kernel.org
CC: kernel-hardening@...ts.openwall.com
CC: linux-mm@...ck.org
CC: linux-kernel@...r.kernel.org
---
security/integrity/ima/ima.h | 3 ++-
security/integrity/ima/ima_policy.c | 9 +++++----
2 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index cc12f3449a72..297c25f5122e 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -24,6 +24,7 @@
#include <linux/hash.h>
#include <linux/tpm.h>
#include <linux/audit.h>
+#include <linux/prmem.h>
#include <crypto/hash_info.h>
#include "../integrity.h"
@@ -50,7 +51,7 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8 };
#define IMA_TEMPLATE_IMA_FMT "d|n"
/* current content of the policy */
-extern int ima_policy_flag;
+extern int ima_policy_flag __wr_after_init;
/* set during initialization */
extern int ima_hash_algo;
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 8bc8a1c8cb3f..d49c545b9cfb 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -48,7 +48,7 @@
#define INVALID_PCR(a) (((a) < 0) || \
(a) >= (FIELD_SIZEOF(struct integrity_iint_cache, measured_pcrs) * 8))
-int ima_policy_flag;
+int ima_policy_flag __wr_after_init;
static int temp_ima_appraise;
static int build_ima_appraise __ro_after_init;
@@ -460,12 +460,13 @@ void ima_update_policy_flag(void)
list_for_each_entry(entry, ima_rules, list) {
if (entry->action & IMA_DO_MASK)
- ima_policy_flag |= entry->action;
+ wr_assign(ima_policy_flag,
+ ima_policy_flag | entry->action);
}
ima_appraise |= (build_ima_appraise | temp_ima_appraise);
if (!ima_appraise)
- ima_policy_flag &= ~IMA_APPRAISE;
+ wr_assign(ima_policy_flag, ima_policy_flag & ~IMA_APPRAISE);
}
static int ima_appraise_flag(enum ima_hooks func)
@@ -651,7 +652,7 @@ void ima_update_policy(void)
list_splice_tail_init_rcu(&ima_temp_rules, policy, synchronize_rcu);
if (ima_rules != policy) {
- ima_policy_flag = 0;
+ wr_assign(ima_policy_flag, 0);
ima_rules = policy;
/*
--
2.19.1
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