linux-kernel - [PATCH v10 26/27] ima: Limit number of policy rules in non-init_ima

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Message-Id: <20220201203735.164593-27-stefanb@linux.ibm.com>
Date:   Tue,  1 Feb 2022 15:37:34 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     zohar@...ux.ibm.com, serge@...lyn.com,
        christian.brauner@...ntu.com, containers@...ts.linux.dev,
        dmitry.kasatkin@...il.com, ebiederm@...ssion.com,
        krzysztof.struczynski@...wei.com, roberto.sassu@...wei.com,
        mpeters@...hat.com, lhinds@...hat.com, lsturman@...hat.com,
        puiterwi@...hat.com, jejb@...ux.ibm.com, jamjoom@...ibm.com,
        linux-kernel@...r.kernel.org, paul@...l-moore.com, rgb@...hat.com,
        linux-security-module@...r.kernel.org, jmorris@...ei.org,
        Stefan Berger <stefanb@...ux.ibm.com>
Subject: [PATCH v10 26/27] ima: Limit number of policy rules in non-init_ima_ns

Limit the number of policy rules one can set in non-init_ima_ns to a
hardcoded 1024 rules. If the user attempts to exceed this limit by
setting too many additional rules, emit an audit message with the cause
'too-many-rules' and simply ignore the newly added rules.

Switch the accounting for the memory allocated for IMA policy rules to
GFP_KERNEL_ACCOUNT so that cgroups kernel memory accounting takes effect.

Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
---
 security/integrity/ima/ima_fs.c     | 20 ++++++++++++++------
 security/integrity/ima/ima_policy.c | 23 ++++++++++++++++++-----
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 58d80884880f..cd102bbd4677 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -410,24 +410,32 @@ static int ima_release_policy(struct inode *inode, struct file *file)
 {
 	struct ima_namespace *ns = &init_ima_ns;
 	const char *cause = ns->valid_policy ? "completed" : "failed";
+	int err = 0;
 
 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 		return seq_release(inode, file);
 
-	if (ns->valid_policy && ima_check_policy(ns) < 0) {
-		cause = "failed";
-		ns->valid_policy = 0;
+	if (ns->valid_policy) {
+		err = ima_check_policy(ns);
+		if (err < 0) {
+			if (err == -ENOSPC)
+				cause = "too-many-rules";
+			else
+				cause = "failed";
+			ns->valid_policy = 0;
+		}
 	}
 
 	pr_info("policy update %s\n", cause);
-	integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
-			    "policy_update", cause, !ns->valid_policy, 0);
+	integrity_audit_message(AUDIT_INTEGRITY_STATUS, NULL, NULL,
+				"policy_update", cause, !ns->valid_policy, 0,
+				-err);
 
 	if (!ns->valid_policy) {
 		ima_delete_rules(ns);
 		ns->valid_policy = 1;
 		clear_bit(IMA_FS_BUSY, &ns->ima_fs_flags);
-		return 0;
+		return err;
 	}
 
 	ima_update_policy(ns);
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index acb4c36e539f..3f84d04f101d 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -305,7 +305,8 @@ static struct ima_rule_opt_list *ima_alloc_rule_opt_list(const substring_t *src)
 		return ERR_PTR(-EINVAL);
 	}
 
-	opt_list = kzalloc(struct_size(opt_list, items, count), GFP_KERNEL);
+	opt_list = kzalloc(struct_size(opt_list, items, count),
+			   GFP_KERNEL_ACCOUNT);
 	if (!opt_list) {
 		kfree(src_copy);
 		return ERR_PTR(-ENOMEM);
@@ -379,7 +380,7 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_namespace *ns,
 	 * Immutable elements are copied over as pointers and data; only
 	 * lsm rules can change
 	 */
-	nentry = kmemdup(entry, sizeof(*nentry), GFP_KERNEL);
+	nentry = kmemdup(entry, sizeof(*nentry), GFP_KERNEL_ACCOUNT);
 	if (!nentry)
 		return NULL;
 
@@ -826,7 +827,7 @@ static void add_rules(struct ima_namespace *ns,
 
 		if (policy_rule & IMA_CUSTOM_POLICY) {
 			entry = kmemdup(&entries[i], sizeof(*entry),
-					GFP_KERNEL);
+					GFP_KERNEL_ACCOUNT);
 			if (!entry)
 				continue;
 
@@ -863,7 +864,7 @@ static int __init ima_init_arch_policy(struct ima_namespace *ns)
 
 	ns->arch_policy_entry = kcalloc(arch_entries + 1,
 					sizeof(*ns->arch_policy_entry),
-					GFP_KERNEL);
+					GFP_KERNEL_ACCOUNT);
 	if (!ns->arch_policy_entry)
 		return 0;
 
@@ -975,8 +976,20 @@ void __init ima_init_policy(struct ima_namespace *ns)
 /* Make sure we have a valid policy, at least containing some rules. */
 int ima_check_policy(struct ima_namespace *ns)
 {
+	struct ima_rule_entry *entry;
+	size_t len1 = 0;
+	size_t len2 = 0;
+
 	if (list_empty(&ns->ima_temp_rules))
 		return -EINVAL;
+	if (ns != &init_ima_ns) {
+		list_for_each_entry(entry, &ns->ima_temp_rules, list)
+			len1++;
+		list_for_each_entry(entry, &ns->ima_policy_rules, list)
+			len2++;
+		if (len1 + len2 > 1024)
+			return -ENOSPC;
+	}
 	return 0;
 }
 
@@ -1848,7 +1861,7 @@ ssize_t ima_parse_add_rule(struct ima_namespace *ns, char *rule)
 	if (*p == '#' || *p == '\0')
 		return len;
 
-	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL_ACCOUNT);
 	if (!entry) {
 		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
 				    NULL, op, "-ENOMEM", -ENOMEM, audit_info);
-- 
2.31.1