linux-kernel - Re: [PATCH] netfilter: avoid warn and OOM on vmalloc call

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Date:   Thu, 1 Dec 2016 10:42:22 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Florian Westphal <fw@...len.de>,
        Neil Horman <nhorman@...driver.com>,
        netdev <netdev@...r.kernel.org>, netfilter-devel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] netfilter: avoid warn and OOM on vmalloc call

On Wed, Nov 30, 2016 at 8:42 PM, Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
> Hi Andrey,
>
> Please let me know how this works for you. It seems good here, though
> your poc may still trigger OOM through other means.

Hi Marcelo,

Don't see any reports with this patch.

Thanks!

>
> Thanks,
> Marcelo
>
> ---8<---
>
> Andrey Konovalov reported that this vmalloc call is based on an
> userspace request and that it's spewing traces, which may flood the logs
> and cause DoS if abused.
>
> Florian Westphal also mentioned that this call should not trigger OOM,
> as kmalloc one is already not triggering it.
>
> This patch brings the vmalloc call in sync to kmalloc and disables the
> warn trace on allocation failure and also disable OOM invocation.
>
> Note, however, that under such stress situation, other places may
> trigger OOM invocation.
>
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
> Cc: Florian Westphal <fw@...len.de>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> ---
>  net/netfilter/x_tables.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index fc4977456c30e098197b4f987b758072c9cf60d9..dece525bf83a0098dad607fce665cd0bde228362 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -958,7 +958,9 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
>         if (sz <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
>                 info = kmalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY);
>         if (!info) {
> -               info = vmalloc(sz);
> +               info = __vmalloc(sz, GFP_KERNEL | __GFP_NOWARN |
> +                                    __GFP_NORETRY | __GFP_HIGHMEM,
> +                                PAGE_KERNEL);
>                 if (!info)
>                         return NULL;
>         }
> --
> 2.9.3
>