linux-kernel - [PATCH] audit: catch errors from audit_filter

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Message-Id: <6c97e8eec7aee6bade82dd0c7933908098846a90.1465934130.git.rgb@redhat.com>
Date:	Tue, 14 Jun 2016 17:03:36 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	linux-audit@...hat.com, linux-kernel@...r.kernel.org
Cc:	Richard Guy Briggs <rgb@...hat.com>, sgrubb@...hat.com,
	pmoore@...hat.com, eparis@...hat.com
Subject: [PATCH] audit: catch errors from audit_filter_rules field checks

In the case of an error returned from a field check in an audit filter
syscall rule, it is treated as a match and the rule action is honoured.

This could cause a rule with a default of NEVER and an selinux field
check error to avoid logging.

Recommend matching with an action of ALWAYS to catch malicious abuse of
this bug.  The downside of this approach is it could DoS the audit
subsystem.

Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
 kernel/auditsc.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 71e14d8..6123672 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -683,6 +683,10 @@ static int audit_filter_rules(struct task_struct *tsk,
 		}
 		if (!result)
 			return 0;
+		if (result < 0) {
+			*state = AUDIT_RECORD_CONTEXT;
+			return 1;
+		}
 	}

 	if (ctx) {
-- 
1.7.1