linux-kernel - [PATCH 13/13] security/integrity/ima: converts stats to seqnum

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Message-Id: <cbc346bbeb306db3effefac0d27c93e143ac0442.1605027593.git.skhan@linuxfoundation.org>
Date:   Tue, 10 Nov 2020 12:53:39 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     zohar@...ux.ibm.com, dmitry.kasatkin@...il.com, jmorris@...ei.org,
        serge@...lyn.com, gregkh@...uxfoundation.org,
        keescook@...omium.org, peterz@...radead.org
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 13/13] security/integrity/ima: converts stats to seqnum_ops

seqnum_ops api is introduced to be used when a variable is used as
a sequence/stat counter and doesn't guard object lifetimes. This
clearly differentiates atomic_t usages that guard object lifetimes.

seqnum32 variables wrap around to INT_MIN when it overflows and
should not be used to guard resource lifetimes, device usage and
open counts that control state changes, and pm states.

atomic_t variables used for eima_htable.violations and number of stored
measurements and ios_threshold are atomic counters, and violations is
only an idicator and can overflow. No chane to the behavior with this
change.

Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 security/integrity/ima/ima.h       | 5 +++--
 security/integrity/ima/ima_api.c   | 2 +-
 security/integrity/ima/ima_fs.c    | 4 ++--
 security/integrity/ima/ima_queue.c | 7 ++++---
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 6ebefec616e4..55fe1d14c67a 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -21,6 +21,7 @@
 #include <linux/tpm.h>
 #include <linux/audit.h>
 #include <crypto/hash_info.h>
+#include <linux/seqnum_ops.h>
 
 #include "../integrity.h"
 
@@ -174,8 +175,8 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
 extern spinlock_t ima_queue_lock;
 
 struct ima_h_table {
-	atomic_long_t len;	/* number of stored measurements in the list */
-	atomic_long_t violations;
+	struct seqnum64 len;	/* number of stored measurements in the list */
+	struct seqnum64 violations;
 	struct hlist_head queue[IMA_MEASURE_HTABLE_SIZE];
 };
 extern struct ima_h_table ima_htable;
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 4f39fb93f278..b1a203435698 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -144,7 +144,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
 	int result;
 
 	/* can overflow, only indicator */
-	atomic_long_inc(&ima_htable.violations);
+	seqnum64_inc(&ima_htable.violations);
 
 	result = ima_alloc_init_template(&event_data, &entry, NULL);
 	if (result < 0) {
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index ea8ff8a07b36..03a78b445052 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -39,12 +39,12 @@ __setup("ima_canonical_fmt", default_canonical_fmt_setup);
 static int valid_policy = 1;
 
 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
-				     loff_t *ppos, atomic_long_t *val)
+				     loff_t *ppos, struct seqnum64 *val)
 {
 	char tmpbuf[32];	/* greater than largest 'long' string value */
 	ssize_t len;
 
-	len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
+	len = scnprintf(tmpbuf, sizeof(tmpbuf), "%lli\n", seqnum64_read(val));
 	return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
 }
 
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index c096ef8945c7..87db50dd1721 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -17,6 +17,7 @@
 
 #include <linux/rculist.h>
 #include <linux/slab.h>
+#include <linux/seqnum_ops.h>
 #include "ima.h"
 
 #define AUDIT_CAUSE_LEN_MAX 32
@@ -33,8 +34,8 @@ static unsigned long binary_runtime_size = ULONG_MAX;
 
 /* key: inode (before secure-hashing a file) */
 struct ima_h_table ima_htable = {
-	.len = ATOMIC_LONG_INIT(0),
-	.violations = ATOMIC_LONG_INIT(0),
+	.len = SEQNUM_INIT(0),
+	.violations = SEQNUM_INIT(0),
 	.queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
 };
 
@@ -106,7 +107,7 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
 	INIT_LIST_HEAD(&qe->later);
 	list_add_tail_rcu(&qe->later, &ima_measurements);
 
-	atomic_long_inc(&ima_htable.len);
+	seqnum64_inc(&ima_htable.len);
 	if (update_htable) {
 		key = ima_hash_key(entry->digests[ima_hash_algo_idx].digest);
 		hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
-- 
2.27.0