selinux: fix double free of cond_list on error paths

On error path from cond_read_list() and duplicate_policydb_cond_list()
the cond_list_destroy() gets called a second time in caller functions,
resulting in NULL pointer deref.  Fix this by resetting the
cond_list_len to 0 in cond_list_destroy(), making subsequent calls a
noop.

Also consistently reset the cond_list pointer to NULL after freeing.

Cc: stable@vger.kernel.org
Signed-off-by: Vratislav Bendel <vbendel@redhat.com>
[PM: fix line lengths in the description]
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index 2ec6e5c..feb206f 100644 (file)
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -152,6 +152,8 @@ static void cond_list_destroy(struct policydb *p)
        for (i = 0; i < p->cond_list_len; i++)
                cond_node_destroy(&p->cond_list[i]);
        kfree(p->cond_list);
+       p->cond_list = NULL;
+       p->cond_list_len = 0;
 }
 
 void cond_policydb_destroy(struct policydb *p)
@@ -441,7 +443,6 @@ int cond_read_list(struct policydb *p, void *fp)
        return 0;
 err:
        cond_list_destroy(p);
-       p->cond_list = NULL;
        return rc;
 }