Subject: Re: [PATCH RESEND] ipv6: return with appropriate error code when sending RH0 using setsockopt()

From: Shan Wei <[email-masked]>
Date: Thu, 04 Sep 2008 11:44:10 +0800

Brian Haley 写道:
> Shan Wei wrote:
>>  I'm sorry to resend the patch, for that no one replied it from Jun 27.
>>
>>  The kernel had removed the RH0(Type 0 Routing Header), but we can still
>>  send IPv6 packet with RH0 using sendmsg() or setsockopt().
>>
>>  Compare with sendmsg() that returns EINVAL, but setsockopt() return EPERM.
>>  The patch fix it.
>>
>> Signed-off-by: Shan Wei <[email-masked]>
>> ---
>>  net/ipv6/ipv6_sockglue.c |    6 ++++--
>>  1 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
>> index 4e5eac3..7a58597 100644
>> --- a/net/ipv6/ipv6_sockglue.c
>> +++ b/net/ipv6/ipv6_sockglue.c
>> @@ -353,9 +353,10 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
>>  			goto e_inval;
>>  
>>  		/* hop-by-hop / destination options are privileged option */
>> -		retv = -EPERM;
>> -		if (optname != IPV6_RTHDR && !capable(CAP_NET_RAW))
>> +		if (optname != IPV6_RTHDR && !capable(CAP_NET_RAW)) {
>> +			retv = -EPERM;
>>  			break;
>> +		}
> 
> I'm not sure you need this since it doesn't actually change anything,
> setting the error before the check just seems like the style in this
> function.  It will get set to -EINVAL below...
> 
For uncommon expection, if the check is true, we set the error. 
it will reduce the number of setting retv value.

>> @@ -365,6 +366,7 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
>>  			break;
>>  		}
>>  
>> +		retv = -EINVAL;
>>  		/* routing header option needs extra check */
>>  		if (optname == IPV6_RTHDR && opt && opt->srcrt) {
>>  			struct ipv6_rt_hdr *rthdr = opt->srcrt;
> 
> This seems correct as trying to set an unsupported routing header type
> is invalid, or trying to set a Type 2 that itself is invalid is bad.
> The Unix I checked does this.
> 
yes 
> There's actually another bug here and in the sendmsg() path in that you
> can set the hdrlen and segments_left fields to be invalid (according to
> RFC3775), as long as the math works out (segments * 2 == length).
> Segments_left should always be 1 and hdrlen 2 for a Type2 routing
> header.  The packet should be dropped at the destination, but we
> probably shouldn't send it.  I can send a patch for that later.
> 
> -Brian
>