[PATCH 5.7 428/477] selinux: fix undefined return of cond_evaluate_expr

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Tom Rix <trix@xxxxxxxxxx>

commit 8231b0b9c322c894594fb42eb0eb9f93544a6acc upstream.

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@xxxxxxxxxxxxxxx
Signed-off-by: Tom Rix <trix@xxxxxxxxxx>
Acked-by: Stephen Smalley <stephen.smalley.work@xxxxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 security/selinux/ss/conditional.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -27,6 +27,9 @@ static int cond_evaluate_expr(struct pol
 	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];