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SubjectRe: [PATCH v4] af_netlink: ensure that NLMSG_DONE never fails in dumps
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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Thu, 9 Nov 2017 13:04:44 +0900

> @@ -2195,13 +2197,15 @@ static int netlink_dump(struct sock *sk)
> return 0;
> }
>
> - nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE, sizeof(len), NLM_F_MULTI);
> - if (!nlh)
> + nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE,
> + sizeof(nlk->dump_done_errno), NLM_F_MULTI);
> + if (WARN_ON(!nlh))
> goto errout_skb;

If you're handling this by forcing another read() to procude the
NLMSG_DONE, then you have no reason to WARN_ON() here.

In fact you are adding a WARN_ON() which is trivially triggerable by
any user.

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