Re: [PATCH] ipvs:set sock send/receive buffer correctly

[linmiaohe]

On 2019/4/17 21:18, Eric Dumazet wrote:
> 
> 
> On 04/17/2019 02:18 AM, linmiaohe wrote:
>> From: Jie Liu <liujie165@xxxxxxxxxx>
>>
>> If we set sysctl_wmem_max or sysctl_rmem_max larger than INT_MAX,
>> the send/receive buffer of sock will be an negative value. Same as
>> when the val is larger than INT_MAX/2.
>>
>> Fixes: 1c003b1580e2 ("ipvs: wakeup master thread")
>> Reported-by: Qiang Ning <ningqiang1@xxxxxxxxxx>
>> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>> Signed-off-by: Jie Liu <liujie165@xxxxxxxxxx>
>> ---
>>  net/netfilter/ipvs/ip_vs_sync.c | 10 ++++------
>>  1 file changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
>> index 2526be6b3d90..c0e4cbed6e74 100644
>> --- a/net/netfilter/ipvs/ip_vs_sync.c
>> +++ b/net/netfilter/ipvs/ip_vs_sync.c
>> @@ -1278,14 +1278,12 @@ static void set_sock_size(struct sock *sk, int mode, int val)
>>  	/* setsockopt(sock, SOL_SOCKET, SO_RCVBUF, &val, sizeof(val)); */
>>  	lock_sock(sk);
>>  	if (mode) {
>> -		val = clamp_t(int, val, (SOCK_MIN_SNDBUF + 1) / 2,
>> -			      sysctl_wmem_max);
>> -		sk->sk_sndbuf = val * 2;
>> +		val = min_t(u32, val, sysctl_wmem_max);
>> +		sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);
> 
> What prevents val * 2 to overflow ? 
> 
> Code in sock_setsockopt() looks quite different.
> .
> 
In fact, I just implemented this function with reference to
sock_setsockopt(). When val * 2 overflow, we will set the
buffer as SOCK_MIN_SNDBUF, just as sock_setsockopt() do.