linux-kernel - [PATCH] lockdown: ratelimit denial messages

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Message-Id: <20220908220222.267255-1-nathanl@linux.ibm.com>
Date:   Thu,  8 Sep 2022 17:02:22 -0500
From:   Nathan Lynch <nathanl@...ux.ibm.com>
To:     linux-security-module@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, paul@...l-moore.com,
        jmorris@...ei.org, serge@...lyn.com
Subject: [PATCH] lockdown: ratelimit denial messages

User space can flood the log with lockdown denial messages:

[  662.555584] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.563237] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.571134] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.578668] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.586021] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.593398] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7

Ratelimiting these shouldn't meaningfully degrade the quality of the
information logged.

Signed-off-by: Nathan Lynch <nathanl@...ux.ibm.com>
---
 security/lockdown/lockdown.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index 87cbdc64d272..a79b985e917e 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -63,7 +63,7 @@ static int lockdown_is_locked_down(enum lockdown_reason what)
 
 	if (kernel_locked_down >= what) {
 		if (lockdown_reasons[what])
-			pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
+			pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
 				  current->comm, lockdown_reasons[what]);
 		return -EPERM;
 	}
-- 
2.37.1