Subject: Re: v3 for tcp friends?

From: Li Yu <[email-masked]>
Date: Wed, 23 Jan 2013 15:58:46 +0800

于 2013年01月23日 15:21, Li Yu 写道:
> 于 2013年01月23日 14:46, Eric Dumazet 写道:
>> On Wed, 2013-01-23 at 14:12 +0800, Li Yu wrote:
>>> Oops, this hang is not since TCP friends patch!
>>>
>>> sk_sndbuf_get() is broken by 32 bits integer overflow
>>> because of so large value in net.ipv4.tcp_{rmem,wmem}.
>>>
>>> but this hang also can be found in net-next.git
>>> (3.8.0-rc3+), if we run below commands, then all new
>>> TCP connections stop working!
>>>
>>> # when TCP friends is disabled
>>> sysctl -w net.ipv4.tcp_rmem="4096 4294967296 4294967296" # 4GB
>>> sysctl -w net.ipv4.tcp_wmem="4096 4294967296 4294967296"
>>
>> Right we need to make sure we dont overflow.
>>
>> Try the following fix :
>>
>> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
>> index a25e1d2..1459145 100644
>> --- a/net/ipv4/sysctl_net_ipv4.c
>> +++ b/net/ipv4/sysctl_net_ipv4.c
>> @@ -549,14 +549,16 @@ static struct ctl_table ipv4_table[] = {
>>           .data        = &sysctl_tcp_wmem,
>>           .maxlen        = sizeof(sysctl_tcp_wmem),
>>           .mode        = 0644,
>> -        .proc_handler    = proc_dointvec
>> +        .extra1        = &zero,
>> +        .proc_handler    = proc_dointvec_minmax
>>       },
>>       {
>>           .procname    = "tcp_rmem",
>>           .data        = &sysctl_tcp_rmem,
>>           .maxlen        = sizeof(sysctl_tcp_rmem),
>>           .mode        = 0644,
>> -        .proc_handler    = proc_dointvec
>> +        .extra1        = &zero,
>> +        .proc_handler    = proc_dointvec_minmax
>>       },
>>       {
>>           .procname    = "tcp_app_win",
>>
>>
>>
> Thanks for so quick reply, I will test it soon.
>
> however I suspect whether this patch could fix overflow if we merged TCP
> friends patch in future.
>

Tested on 3.7.0-rc1+, but bug is still alive
with disabled TCP friends ...

Thanks

Yu

> With TCP friends, we have source like below, or TCP friends should care
> this ?
>
> static inline int sk_sndbuf_get(const struct sock *sk)
> {
>          if (sk->sk_friend)
>                  return sk->sk_sndbuf + sk->sk_friend->sk_rcvbuf;
>          else
>                  return sk->sk_sndbuf;
> }
>
> static inline bool sk_stream_memory_free(const struct sock *sk)
> {
>          return sk_wmem_queued_get(sk) < sk_sndbuf_get(sk);
> }
>
> So sk_sndbuf_get() still may be overflow when we have right value in
> net.ipv4.tcp_{rmem,wmem}.
>
> Thanks