netdev - Re: [PATCH net] ipv4: Fix potential uninit variable access buf in __ip_make

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Date:   Fri, 7 Apr 2023 08:54:09 +0800
From:   "Ziyang Xuan (William)" <william.xuanziyang@...wei.com>
To:     Eric Dumazet <edumazet@...gle.com>
CC:     <davem@...emloft.net>, <dsahern@...nel.org>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        <dlstevens@...ibm.com>
Subject: Re: [PATCH net] ipv4: Fix potential uninit variable access buf in
 __ip_make_skb()

> On Thu, Apr 6, 2023 at 5:11 AM Ziyang Xuan
> <william.xuanziyang@...wei.com> wrote:
>>
>> Like commit ea30388baebc ("ipv6: Fix an uninit variable access bug in
>> __ip6_make_skb()"). icmphdr does not in skb linear region under the
>> scenario of SOCK_RAW socket. Access icmp_hdr(skb)->type directly will
>> trigger the uninit variable access bug.
>>
>> Use a local variable icmp_type to carry the correct value in different
>> scenarios.
>>
>> Fixes: 96793b482540 ("[IPV4]: Add ICMPMsgStats MIB (RFC 4293)")
>> Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.com>
>> ---
>>  net/ipv4/ip_output.c | 12 +++++++++---
>>  1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
>> index 4e4e308c3230..57921b297a8e 100644
>> --- a/net/ipv4/ip_output.c
>> +++ b/net/ipv4/ip_output.c
>> @@ -1570,9 +1570,15 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
>>         cork->dst = NULL;
>>         skb_dst_set(skb, &rt->dst);
>>
>> -       if (iph->protocol == IPPROTO_ICMP)
>> -               icmp_out_count(net, ((struct icmphdr *)
>> -                       skb_transport_header(skb))->type);
>> +       if (iph->protocol == IPPROTO_ICMP) {
>> +               u8 icmp_type;
>> +
>> +               if (sk->sk_socket->type == SOCK_RAW && !inet_sk(sk)->hdrincl)
> 
> What is the reason for not using sk->sk_type ?

sk->sk_type is more concise. Thank you!

> 
>> +                       icmp_type = fl4->fl4_icmp_type;
>> +               else
>> +                       icmp_type = icmp_hdr(skb)->type;
>> +               icmp_out_count(net, icmp_type);
>> +       }
> 
> 
>>
>>         ip_cork_release(cork);
>>  out:
>> --
>> 2.25.1
>>
> .
>