linux-kernel - [PATCH] selinux: fix undefined return of cond_evaluate

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Date:   Wed, 17 Jun 2020 05:40:28 -0700
From:   trix@...hat.com
To:     paul@...l-moore.com, stephen.smalley.work@...il.com,
        eparis@...isplace.org, omosnace@...hat.com, weiyongjun1@...wei.com
Cc:     selinux@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] selinux: fix undefined return of cond_evaluate_expr

From: Tom Rix <trix@...hat.com>

clang static analysis reports an undefined return

security/selinux/ss/conditional.c:79:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
        return s[0];
        ^~~~~~~~~~~

static int cond_evaluate_expr( ...
{
	u32 i;
	int s[COND_EXPR_MAXDEPTH];

	for (i = 0; i < expr->len; i++)
	  ...

	return s[0];

When expr->len is 0, the loop which sets s[0] never runs.

So return -1 if the loop never runs.

Signed-off-by: Tom Rix <trix@...hat.com>
---
 security/selinux/ss/conditional.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index 450bc02f4cd2..0cc7cdd58465 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -27,6 +27,9 @@ static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
 	int s[COND_EXPR_MAXDEPTH];
 	int sp = -1;
 
+	if (expr->len == 0)
+		return -1;
+
 	for (i = 0; i < expr->len; i++) {
 		struct cond_expr_node *node = &expr->nodes[i];
 
-- 
2.18.1