linux-kernel - Re: [PATCH net-next] net/smc: cast sizeof to int for comparison

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Message-ID: <c50b9154-e72b-437b-d0c4-40f2b8943c65@huawei.com>
Date:   Mon, 17 Sep 2018 17:38:41 +0800
From:   YueHaibing <yuehaibing@...wei.com>
To:     Ursula Braun <ubraun@...ux.ibm.com>
CC:     <davem@...emloft.net>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-s390@...r.kernel.org>
Subject: Re: [PATCH net-next] net/smc: cast sizeof to int for comparison


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@...wei.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?

> 
> Regards, Ursula
> 
> 
>