From: Jakub Kicinski <kuba@kernel.org>
To: Chenguang Zhao <zhaochenguang@kylinos.cn>
Cc: Paul Moore <paul@paul-moore.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org, linux-security-module@vger.kernel.org
Subject: Re: [PATCH net v2] netlabel: validate unlabeled mask attribute length
Date: Mon, 1 Jun 2026 19:38:05 -0700 [thread overview]
Message-ID: <20260601193805.011c7f15@kernel.org> (raw)
In-Reply-To: <20260528015913.190970-1-zhaochenguang@kylinos.cn>
On Thu, 28 May 2026 09:59:13 +0800 Chenguang Zhao wrote:
> netlbl_unlabel_addrinfo_get() checked the address length
> but allowed shorter mask attributes to pass through to
> fixed-size address reads.
>
> netlbl_unlabel_addrinfo_get() only rejected a mask
> length mismatch when the address attribute length
> was also invalid. A crafted Generic Netlink request
> could therefore provide a valid IPv4/IPv6 address
> attribute with a shorter mask attribute.
>
> NLA_BINARY policy lengths are maximum lengths,
> not exact lengths, so the short mask can pass
> policy validation. The mask is later read as
> a full struct in_addr or struct in6_addr.
> Require both address and mask attributes to
> have the exact expected size.
Sorry, didn't look at this until Paul responded.
NLA_BINARY does _default_ to maximum lengths.
But you can use NLA_POLICY_EXACT_LEN() to have the policy do the right
thing. Using the policy is preferred - less code, and policy
introspection informs user space about the expectations.
--
pw-bot: cr
next prev parent reply other threads:[~2026-06-02 2:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-28 1:59 [PATCH net v2] netlabel: validate unlabeled mask attribute length Chenguang Zhao
2026-06-02 2:25 ` Paul Moore
2026-06-02 2:38 ` Jakub Kicinski [this message]
2026-06-02 3:08 ` Paul Moore
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