netdev - Re: [PATCH net-next] rtnetlink: Fix null-ptr-deref in rtnl

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Message-ID: <CANn89iKuLWFf_pCBmiDr1E+3WZxxm1nvu0FJjB9k256EFZqP6w@mail.gmail.com>
Date:   Fri, 1 Jun 2018 04:26:26 -0400
From:   Eric Dumazet <edumazet@...gle.com>
To:     bhole_prashant_q7@....ntt.co.jp
Cc:     David Miller <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Florian Westphal <fw@...len.de>,
        netdev <netdev@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH net-next] rtnetlink: Fix null-ptr-deref in rtnl_newlink

On Fri, Jun 1, 2018 at 4:18 AM Prashant Bhole
<bhole_prashant_q7@....ntt.co.jp> wrote:
>
> In rtnl_newlink(), NULL check is performed on m_ops however member of
> ops is accessed. Fixed by accessing member of m_ops instead of ops.
>
> [  345.432629] BUG: KASAN: null-ptr-deref in rtnl_newlink+0x400/0x1110
> [  345.432629] Read of size 4 at addr 0000000000000088 by task ip/986
> [  345.432629]
> [  345.432629] CPU: 1 PID: 986 Comm: ip Not tainted 4.17.0-rc6+ #9
> [  345.432629] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> [  345.432629] Call Trace:
> [  345.432629]  dump_stack+0xc6/0x150
> [  345.432629]  ? dump_stack_print_info.cold.0+0x1b/0x1b
> [  345.432629]  ? kasan_report+0xb4/0x410
> [  345.432629]  kasan_report.cold.4+0x8f/0x91
> [  345.432629]  ? rtnl_newlink+0x400/0x1110
> [  345.432629]  rtnl_newlink+0x400/0x1110
> [...]
>
> Fixes: ccf8dbcd062a ("rtnetlink: Remove VLA usage")
> Signed-off-by: Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
> ---
>  net/core/rtnetlink.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 8ca49a0e13fb..9a1ba2015ad8 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -2936,7 +2936,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
>                 }
>
>                 if (m_ops) {
> -                       if (ops->slave_maxtype > RTNL_SLAVE_MAX_TYPE)
> +                       if (m_ops->slave_maxtype > RTNL_SLAVE_MAX_TYPE)
>                                 return -EINVAL;


Oh nice

CC Kees Cook.