netdev - Re: [PATCH] genetlink: fix unsigned int comparison with less than zero

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Date:   Sat, 12 Nov 2016 22:37:16 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Colin King <colin.king@...onical.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        pravin shelar <pshelar@....org>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Florian Westphal <fw@...len.de>,
        Tycho Andersen <tycho.andersen@...onical.com>,
        Tom Herbert <tom@...bertland.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] genetlink: fix unsigned int comparison with less than
 zero

On Thu, 2016-11-10 at 09:11 -0800, Cong Wang wrote:
> On Thu, Nov 10, 2016 at 7:57 AM, Colin King <colin.king@...onical.com
> > wrote:
> > 
> > From: Colin Ian King <colin.king@...onical.com>
> > 
> > family->id is unsigned, so the less than zero check for
> > failure return from idr_alloc is never true and so the error exit
> > is never handled.  Instead, assign err and check if this is less
> > than zero since this is a signed integer.
> 
> Why family->id can't be just signed int? For me it should be.

I suppose it could be, since family IDs are allocated in a 16-bit range
anyway. But family IDs can also never actually be negative, so having
an unsigned int in the struct makes sense too.

I tend to think this patch is fine.

johannes