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Subject: Re: [PATCH net-next] net/smc: cast sizeof to int for comparison
To:     YueHaibing <yuehaibing@huawei.com>
Cc:     davem@davemloft.net, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, linux-s390@vger.kernel.org
References: <20180915100036.20100-1-yuehaibing@huawei.com>
 <554a145a-d59d-9033-1702-4987a9c4bc94@linux.ibm.com>
 <c50b9154-e72b-437b-d0c4-40f2b8943c65@huawei.com>
From:   Ursula Braun <ubraun@linux.ibm.com>
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Date:   Mon, 17 Sep 2018 13:49:10 +0200
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On 09/17/2018 11:38 AM, YueHaibing wrote:
> 
> On 2018/9/17 16:49, Ursula Braun wrote:
>>
>>
>> On 09/15/2018 12:00 PM, YueHaibing wrote:
>>> Comparing an int to a size, which is unsigned, causes the int to become
>>> unsigned, giving the wrong result. kernel_sendmsg can return a negative
>>> error code.
>>>
>>
>> Thanks for reporting this issue!
>>
>>> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
>>> ---
>>>  net/smc/smc_clc.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
>>> index 83aba9a..fd0f5ce 100644
>>> --- a/net/smc/smc_clc.c
>>> +++ b/net/smc/smc_clc.c
>>> @@ -446,7 +446,7 @@ int smc_clc_send_proposal(struct smc_sock *smc, int smc_type,
>>>  	vec[i++].iov_len = sizeof(trl);
>>>  	/* due to the few bytes needed for clc-handshake this cannot block */
>>>  	len = kernel_sendmsg(smc->clcsock, &msg, vec, i, plen);
>>> -	if (len < sizeof(pclc)) {
>>> +	if (len < (int)sizeof(pclc)) {
>>>  		if (len >= 0) {
>>>  			reason_code = -ENETUNREACH;
>>>  			smc->sk.sk_err = -reason_code;
>>>
>>
>> Your fix helps, but I would like to follow the hint of Andreas Schwab, and split
>> the return value check like this:
>>
>> ---
>>  net/smc/smc_clc.c |   14 ++++++--------
>>  1 file changed, 6 insertions(+), 8 deletions(-)
>>
>> --- a/net/smc/smc_clc.c
>> +++ b/net/smc/smc_clc.c
>> @@ -446,14 +446,12 @@ int smc_clc_send_proposal(struct smc_soc
>>  	vec[i++].iov_len = sizeof(trl);
>>  	/* due to the few bytes needed for clc-handshake this cannot block */
>>  	len = kernel_sendmsg(smc->clcsock, &msg, vec, i, plen);
>> -	if (len < sizeof(pclc)) {
>> -		if (len >= 0) {
>> -			reason_code = -ENETUNREACH;
>> -			smc->sk.sk_err = -reason_code;
>> -		} else {
>> -			smc->sk.sk_err = smc->clcsock->sk->sk_err;
>> -			reason_code = -smc->sk.sk_err;
>> -		}
>> +	if (len < 0) {
>> +		smc->sk.sk_err = smc->clcsock->sk->sk_err;
>> +		reason_code = -smc->sk.sk_err;
>> +	} else if (len < (int)sizeof(pclc)) {
>> +		reason_code = -ENETUNREACH;
>> +		smc->sk.sk_err = -reason_code;
>>  	}
>>  
>>  	return reason_code;
>>
>> Agreed?
> 
> Yes, Need a new patch from me?
> 

Not necessary, I will make sure this patch version is added to the smc code.

>>
>> Regards, Ursula
>>
>>
>>
>