[PATCH v2 1/1] selinux: fix another double free

[trix]

From: Tom Rix <t...@redhat.com>

Clang static analysis reports this double free error

security/selinux/ss/conditional.c:139:2: warning: Attempt to free released 
memory [unix.Malloc]
        kfree(node->expr.nodes);
        ^~~~~~~~~~~~~~~~~~~~~~~

When cond_read_node fails, it calls cond_node_destroy which frees the
node but does not poison the entry in the node list.  So when it
returns to its caller cond_read_list, cond_read_list deletes the
partial list.  The latest entry in the list will be deleted twice.

So instead of freeing the node in cond_read_node, let list freeing in
code_read_list handle the freeing the problem node along with all of the
earlier nodes.

Because cond_read_node no longer does any error handling, the goto's
the error case are redundant.  Instead just return the error code.

Fixes a problem was introduced by commit

  selinux: convert cond_list to array

Signed-off-by: Tom Rix <t...@redhat.com>
---
 security/selinux/ss/conditional.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/security/selinux/ss/conditional.c 
b/security/selinux/ss/conditional.c
index da94a1b4bfda..d0d6668709f0 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -392,26 +392,21 @@ static int cond_read_node(struct policydb *p, struct 
cond_node *node, void *fp)
 
                rc = next_entry(buf, fp, sizeof(u32) * 2);
                if (rc)
-                       goto err;
+                       return rc;
 
                expr->expr_type = le32_to_cpu(buf[0]);
                expr->bool = le32_to_cpu(buf[1]);
 
                if (!expr_node_isvalid(p, expr)) {
                        rc = -EINVAL;
-                       goto err;
+                       return rc;
                }
        }
 
        rc = cond_read_av_list(p, fp, &node->true_list, NULL);
        if (rc)
-               goto err;
+               return rc;
        rc = cond_read_av_list(p, fp, &node->false_list, &node->true_list);
-       if (rc)
-               goto err;
-       return 0;
-err:
-       cond_node_destroy(node);
        return rc;
 }
 
-- 
2.18.1