selinux: fix undefined return of cond_evaluate_expr

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.

Cc: stable@vger.kernel.org
Signed-off-by: Tom Rix <trix@redhat.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index 4867dfc5337ac17ee7e803918d7c20b382f6fb56..7a92b028f7223c39d880e247629d2d88d9ede04f 100644 (file)
--- 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];