selinux: fix NULL dereference in policydb_destroy()

mainline inclusion
from master
commit 6a1afffb
category: bugfix
bugzilla: 120851
CVE: NA

---------------------------

The conversion to kvmalloc() forgot to account for the possibility that
p->type_attr_map_array might be null in policydb_destroy().

Fix this by destroying its contents only if it is not NULL.

Also make sure ebitmap_init() is called on all entries before
policydb_destroy() can be called. Right now this is a no-op, because
both kvcalloc() and ebitmap_init() just zero out the whole struct, but
let's rather not rely on a specific implementation.

Reported-by:  <syzbot+a57b2aff60832666fc28@syzkaller.appspotmail.com>
Fixes: acdf52d9 ("selinux: convert to kvmalloc")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Wang Weiyang <wangweiyang2@huawei.com>
Conflicts:
	security/selinux/ss/policydb.c
	[ acdf52d9 is not applied so only half of this commit is used ]
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>