linux-kernel - [PATCH] tomoyo: Check exceeded quota early in tomoyo_domain_quota_is

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Message-Id: <20211214094526.2442154-1-dvyukov@google.com>
Date:   Tue, 14 Dec 2021 10:45:26 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     takedakn@...data.co.jp, penguin-kernel@...ove.SAKURA.ne.jp,
        jmorris@...ei.org, serge@...lyn.com
Cc:     nogikh@...gle.com, Dmitry Vyukov <dvyukov@...gle.com>,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] tomoyo: Check exceeded quota early in tomoyo_domain_quota_is_ok().

If tomoyo is used in a testing/fuzzing environment in learning mode,
for lots of domains the quota will be exceeded and stay exceeded
for prolonged periods of time. In such cases it's pointless (and slow)
to walk the whole acl list again and again just to rediscover that
the quota is exceeded. We already have the TOMOYO_DIF_QUOTA_WARNED flag
that notes the overflow condition. Check it early to avoid the slowdown.

Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
Cc: linux-security-module@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 security/tomoyo/util.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/security/tomoyo/util.c b/security/tomoyo/util.c
index 1da2e3722b126..af8cd2af3466d 100644
--- a/security/tomoyo/util.c
+++ b/security/tomoyo/util.c
@@ -1051,6 +1051,8 @@ bool tomoyo_domain_quota_is_ok(struct tomoyo_request_info *r)
 		return false;
 	if (!domain)
 		return true;
+	if (READ_ONCE(domain->flags[TOMOYO_DIF_QUOTA_WARNED]))
+		return false;
 	list_for_each_entry_rcu(ptr, &domain->acl_info_list, list,
 				srcu_read_lock_held(&tomoyo_ss)) {
 		u16 perm;
@@ -1096,14 +1098,12 @@ bool tomoyo_domain_quota_is_ok(struct tomoyo_request_info *r)
 	if (count < tomoyo_profile(domain->ns, domain->profile)->
 	    pref[TOMOYO_PREF_MAX_LEARNING_ENTRY])
 		return true;
-	if (!domain->flags[TOMOYO_DIF_QUOTA_WARNED]) {
-		domain->flags[TOMOYO_DIF_QUOTA_WARNED] = true;
-		/* r->granted = false; */
-		tomoyo_write_log(r, "%s", tomoyo_dif[TOMOYO_DIF_QUOTA_WARNED]);
+	WRITE_ONCE(domain->flags[TOMOYO_DIF_QUOTA_WARNED], true);
+	/* r->granted = false; */
+	tomoyo_write_log(r, "%s", tomoyo_dif[TOMOYO_DIF_QUOTA_WARNED]);
 #ifndef CONFIG_SECURITY_TOMOYO_INSECURE_BUILTIN_SETTING
-		pr_warn("WARNING: Domain '%s' has too many ACLs to hold. Stopped learning mode.\n",
-			domain->domainname->name);
+	pr_warn("WARNING: Domain '%s' has too many ACLs to hold. Stopped learning mode.\n",
+		domain->domainname->name);
 #endif
-	}
 	return false;
 }

base-commit: 5472f14a37421d1bca3dddf33cabd3bd6dbefbbc
-- 
2.34.1.173.g76aa8bc2d0-goog