netdev - Re: [PATCH] netfilter: fix int overflow in xt_alloc_table

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Message-ID: <CACT4Y+a5Tvu8XSSLKE-aUiz5=qbJ0fRmt=Q5yCj+bShc8OYpTA@mail.gmail.com>
Date:   Sat, 6 Jan 2018 15:07:06 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>,
        David Miller <davem@...emloft.net>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] netfilter: fix int overflow in xt_alloc_table_info()

On Thu, Dec 28, 2017 at 9:48 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> syzkaller triggered OOM kills by passing ipt_replace.size = -1
> to IPT_SO_SET_REPLACE. The root cause is that SMP_ALIGN() in
> xt_alloc_table_info() causes int overflow and the size check passes
> when it should not. SMP_ALIGN() is no longer needed leftover.
>
> Remove SMP_ALIGN() call in xt_alloc_table_info().
>
> Reported-by: syzbot+4396883fa8c4f64e0175@...kaller.appspotmail.com
> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Pablo Neira Ayuso <pablo@...filter.org>
> Cc: Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
> Cc: Florian Westphal <fw@...len.de>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: netfilter-devel@...r.kernel.org
> Cc: coreteam@...filter.org
> Cc: netdev@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  net/netfilter/x_tables.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index 55802e97f906..e02a21549c99 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -39,7 +39,6 @@ MODULE_LICENSE("GPL");
>  MODULE_AUTHOR("Harald Welte <laforge@...filter.org>");
>  MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");
>
> -#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))
>  #define XT_PCPU_BLOCK_SIZE 4096
>
>  struct compat_delta {
> @@ -1000,7 +999,7 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
>                 return NULL;
>
>         /* Pedantry: prevent them from hitting BUG() in vmalloc.c --RR */
> -       if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages)
> +       if ((size >> PAGE_SHIFT) + 2 > totalram_pages)
>                 return NULL;
>
>         info = kvmalloc(sz, GFP_KERNEL);


Ping.

Dave, will this go into net/net-next?