linux-kernel - Re: [net-ipv4] question about arguments position

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Date:   Thu, 04 May 2017 14:00:15 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Joe Perches <joe@...ches.com>
Cc:     David Miller <davem@...emloft.net>, kuznet@....inr.ac.ru,
        jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-ipv4] question about arguments position

Hi Joe,

Quoting Joe Perches <joe@...ches.com>:

> On Thu, 2017-05-04 at 12:46 -0400, David Miller wrote:
>> From: "Gustavo A. R. Silva" <garsilva@...eddedor.com>
>> Date: Thu, 04 May 2017 11:07:54 -0500
>>
>> > While looking into Coverity ID 1357474 I ran into the following piece
>> > of code at net/ipv4/inet_diag.c:392:
>>
>> Because it's been this way since at least 2005, it doesn't matter if
>> the order is correct or not.  What's there is the locked in behavior
>> exposed to userspace and changing it will break things for people.
>
> Adding a few comments around the code about why
> it is this way will help avoid future questions.

In the case of Coverity, I already triaged and documented this issue.  
So people can ignore it in the future.

Regarding the code comments, what about the following patch:

diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 3828b3a..7a56641 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -389,6 +389,12 @@ static int sk_diag_fill(struct sock *sk, struct  
sk_buff *skb,
                                   nlmsg_flags, unlh, net_admin);
  }

+/*
+ * Ignore the position of the arguments req->id.idiag_dport and
+ * req->id.idiag_sport in both calls to inet_lookup() and inet6_lookup()
+ * functions, once this is a locked in behavior exposed to user space.
+ * Changing this will break things for people.
+ */
  struct sock *inet_diag_find_one_icsk(struct net *net,
                                      struct inet_hashinfo *hashinfo,
                                      const struct inet_diag_req_v2 *req)

Thanks
--
Gustavo A. R. Silva