linux-kernel - [PATCH -next,v3 2/2] audit: return early if the rule has a lower priority

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Date:   Sat, 16 Oct 2021 15:23:51 +0800
From:   Gaosheng Cui <cuigaosheng1@...wei.com>
To:     <paul@...l-moore.com>, <eparis@...hat.com>, <rgb@...hat.com>
CC:     <linux-audit@...hat.com>, <linux-kernel@...r.kernel.org>,
        <wangweiyang2@...wei.com>
Subject: [PATCH -next,v3 2/2] audit: return early if the rule has a lower priority

It is not necessary for audit_filter_rules() functions to check
audit fileds of the rule with a lower priority, and if we did,
there might be some unintended effects, such as the ctx->ppid
may be changed unexpectedly, so return early if the rule has
a lower priority.

Signed-off-by: Gaosheng Cui <cuigaosheng1@...wei.com>
---
 kernel/auditsc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 42d4a4320526..b517947bfa48 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -470,6 +470,9 @@ static int audit_filter_rules(struct task_struct *tsk,
 	u32 sid;
 	unsigned int sessionid;
 
+	if (ctx && rule->prio <= ctx->prio)
+		return 0;
+
 	cred = rcu_dereference_check(tsk->cred, tsk == current || task_creation);
 
 	for (i = 0; i < rule->field_count; i++) {
@@ -737,8 +740,6 @@ static int audit_filter_rules(struct task_struct *tsk,
 	}
 
 	if (ctx) {
-		if (rule->prio <= ctx->prio)
-			return 0;
 		if (rule->filterkey) {
 			kfree(ctx->filterkey);
 			ctx->filterkey = kstrdup(rule->filterkey, GFP_ATOMIC);
-- 
2.30.0