netdev - Re: [PATCH net] net: sit: fix UBSAN Undefined behaviour in check

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190311.103037.1736601922338617214.davem@davemloft.net>
Date:   Mon, 11 Mar 2019 10:30:37 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     linmiaohe@...wei.com
Cc:     kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingfangsen@...wei.com
Subject: Re: [PATCH net] net: sit: fix UBSAN Undefined behaviour in
 check_6rd

From: David Miller <davem@...emloft.net>
Date: Mon, 11 Mar 2019 10:29:37 -0700 (PDT)

> From: linmiaohe <linmiaohe@...wei.com>
> Date: Mon, 11 Mar 2019 16:29:32 +0800
> 
>> @@ -778,8 +778,9 @@ static bool check_6rd(struct ip_tunnel *tunnel, const struct in6_addr *v6dst,
>>  		pbw0 = tunnel->ip6rd.prefixlen >> 5;
>>  		pbi0 = tunnel->ip6rd.prefixlen & 0x1f;
>> 
>> -		d = (ntohl(v6dst->s6_addr32[pbw0]) << pbi0) >>
>> -		    tunnel->ip6rd.relay_prefixlen;
>> +		d = tunnel->ip6rd.relay_prefixlen < 32 ?
>> +			(ntohl(v6dst->s6_addr32[pbw0]) << pbi0) >>
>> +		    tunnel->ip6rd.relay_prefixlen : 0;
>> 
> 
> I hate the fact that we have to guard against something which the rest
> of the code makes sure NEVER EVER happens.
> 
> Every assignment of ->relay_prefixlen is guarded by a check against 32.

Sorry, I now understand, it can equal 32.

I'll apply this, thank you.