linux-kernel - Re: [PATCH][net-next] ipv6: fix incorrect bitwise operator used on rt6i

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Date:   Tue, 10 Oct 2017 11:23:41 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     Martin KaFai Lau <kafai@...com>,
        Colin King <colin.king@...onical.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][net-next] ipv6: fix incorrect bitwise operator used on rt6i_flags

On Tue, Oct 10, 2017 at 11:10 AM, Martin KaFai Lau <kafai@...com> wrote:
> On Tue, Oct 10, 2017 at 05:55:27PM +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> The use of the | operator always leads to true on the expression
>> (rt->rt6i_flags | RTF_CACHE) which looks rather suspect to me. I
>> believe this is fixed by using & instead to just check the
>> RTF_CACHE entry bit.
> Good catch. LGTM. If rt does not have RTF_CACHE set, it should not be in the
> exception table.
>
> Acked-by: Martin KaFai Lau <kafai@...com>
>

Thanks a lot for catching this. Yes. It should have been '&' instead of '|'.

Acked-by: Wei Wang <weiwan@...gle.com>

>>
>> Detected by CoverityScan, CID#1457747 ("Wrong operator used")
>>
>> Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  net/ipv6/route.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index 6db1541eaa7b..0556d1ee189c 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -1425,7 +1425,7 @@ int rt6_remove_exception_rt(struct rt6_info *rt)
>>       int err;
>>
>>       if (!from ||
>> -         !(rt->rt6i_flags | RTF_CACHE))
>> +         !(rt->rt6i_flags & RTF_CACHE))
>>               return -EINVAL;
>>
>>       if (!rcu_access_pointer(from->rt6i_exception_bucket))
>> --
>> 2.14.1
>>