netdev - Re: [Patch nf v2 1/3] xt_hashlimit: avoid OOM for user-controlled vmalloc

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Message-ID: <20200203121612.GR795@breakpoint.cc>
Date:   Mon, 3 Feb 2020 13:16:12 +0100
From:   Florian Westphal <fw@...len.de>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, fw@...len.de,
        netfilter-devel@...r.kernel.org,
        syzbot+adf6c6c2be1c3a718121@...kaller.appspotmail.com,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>
Subject: Re: [Patch nf v2 1/3] xt_hashlimit: avoid OOM for user-controlled
 vmalloc

Cong Wang <xiyou.wangcong@...il.com> wrote:
> The hashtable size could be controlled by user, so use flags
> GFP_USER | __GFP_NOWARN to avoid OOM warning triggered by user-space.
> 
> Also add __GFP_NORETRY to avoid retrying, as this is just a
> best effort and the failure is already handled gracefully.
> 
> Reported-and-tested-by: syzbot+adf6c6c2be1c3a718121@...kaller.appspotmail.com
> Cc: Pablo Neira Ayuso <pablo@...filter.org>
> Cc: Jozsef Kadlecsik <kadlec@...filter.org>
> Cc: Florian Westphal <fw@...len.de>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---
>  net/netfilter/xt_hashlimit.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
> index bccd47cd7190..5d9943b37c42 100644
> --- a/net/netfilter/xt_hashlimit.c
> +++ b/net/netfilter/xt_hashlimit.c
> @@ -293,8 +293,8 @@ static int htable_create(struct net *net, struct hashlimit_cfg3 *cfg,
>  		if (size < 16)
>  			size = 16;
>  	}
> -	/* FIXME: don't use vmalloc() here or anywhere else -HW */
> -	hinfo = vmalloc(struct_size(hinfo, hash, size));
> +	hinfo = __vmalloc(struct_size(hinfo, hash, size),
> +			  GFP_USER | __GFP_NOWARN | __GFP_NORETRY, PAGE_KERNEL);

Sorry for not noticing this earlier: should that be GFP_KERNEL_ACCOUNT
instead of GFP_USER?