[PATCH 11/12] IMA: turn ima_policy_flags into __wr_after_init
From: Igor Stoppa <hidden>
Date: 2018-12-21 18:15:15
Also in:
linux-mm, lkml
Subsystem:
extended verification module (evm), integrity measurement architecture (ima), security subsystem, the rest · Maintainers:
Mimi Zohar, Roberto Sassu, Dmitry Kasatkin, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
Possibly related (same subject, not in this thread)
- 2018-12-20 · Re: [PATCH 11/12] IMA: turn ima_policy_flags into __wr_after_init · Igor Stoppa <hidden>
- 2018-12-20 · Re: [PATCH 11/12] IMA: turn ima_policy_flags into __wr_after_init · Thiago Jung Bauermann <hidden>
- 2018-12-19 · [PATCH 11/12] IMA: turn ima_policy_flags into __wr_after_init · Igor Stoppa <hidden>
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 <redacted> CC: Andy Lutomirski <luto@amacapital.net> CC: Nadav Amit <redacted> CC: Matthew Wilcox <willy@infradead.org> CC: Peter Zijlstra <peterz@infradead.org> CC: Kees Cook <redacted> CC: Dave Hansen <dave.hansen@linux.intel.com> CC: Mimi Zohar <redacted> CC: Thiago Jung Bauermann <redacted> CC: Ahmed Soliman <redacted> CC: linux-integrity@vger.kernel.org CC: kernel-hardening@lists.openwall.com CC: linux-mm@kvack.org CC: linux-kernel@vger.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 7489cb7de6dc..2004de818d92 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c@@ -47,7 +47,7 @@ #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;
@@ -452,12 +452,13 @@ 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)
@@ -574,7 +575,7 @@ 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; } ima_update_policy_flag();
--
2.19.1