netdev - Re: [PATCH] net: af_packet: Validate parameter size for PACKET

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Message-Id: <20130227.152630.35846741651175869.davem@davemloft.net>
Date:	Wed, 27 Feb 2013 15:26:30 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	dborkman@...hat.com
Cc:	linux@...ck-us.net, netdev@...r.kernel.org
Subject: Re: [PATCH] net: af_packet: Validate parameter size for
 PACKET_HDRLEN control message

From: Daniel Borkmann <dborkman@...hat.com>
Date: Wed, 27 Feb 2013 21:22:17 +0100

> On 02/27/2013 08:46 PM, Guenter Roeck wrote:
>> Building af_packet may fail with
>>
>> In function ‘copy_from_user’,
>>      inlined from ‘packet_getsockopt’ at
>>      net/packet/af_packet.c:3215:21:
>> arch/x86/include/asm/uaccess_32.h:211:26: error: call to
>>      ‘copy_from_user_overflow’ declared with attribute error:
>>      copy_from_user()
>>      buffer size is not provably correct
>>
>> if built with W=1 due to a missing parameter size validation.
>>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>>   net/packet/af_packet.c |    2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
>> index c7bfeff..1976b23 100644
>> --- a/net/packet/af_packet.c
>> +++ b/net/packet/af_packet.c
>> @@ -3210,6 +3210,8 @@ static int packet_getsockopt(struct socket
>> *sock, int level, int optname,
>>   		val = po->tp_version;
>>   		break;
>>   	case PACKET_HDRLEN:
>> +		if (len < sizeof(int))
>> +			return -EINVAL;
> 
> I think this could break some user space applications here, those who
> e.g. only pass
> an uint16_t to packet_getsockopt with PACKET_HDRLEN.

Well, their shit is broken on big endian then.