netdev - Re: [Patch net 0/3] idr: fix overflow cases on 32-bit CPU

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Message-ID: <20190702023730.GA1729@bombadil.infradead.org>
Date:   Mon, 1 Jul 2019 19:37:30 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     David Miller <davem@...emloft.net>
Cc:     xiyou.wangcong@...il.com, netdev@...r.kernel.org,
        dcaratti@...hat.com, chrism@...lanox.com
Subject: Re: [Patch net 0/3] idr: fix overflow cases on 32-bit CPU

On Mon, Jul 01, 2019 at 07:16:00PM -0700, David Miller wrote:
> From: Cong Wang <xiyou.wangcong@...il.com>
> Date: Fri, 28 Jun 2019 11:03:40 -0700
> 
> > idr_get_next_ul() is problematic by design, it can't handle
> > the following overflow case well on 32-bit CPU:
> > 
> > u32 id = UINT_MAX;
> > idr_alloc_u32(&id);
> > while (idr_get_next_ul(&id) != NULL)
> >  id++;
> > 
> > when 'id' overflows and becomes 0 after UINT_MAX, the loop
> > goes infinite.
> > 
> > Fix this by eliminating external users of idr_get_next_ul()
> > and migrating them to idr_for_each_entry_continue_ul(). And
> > add an additional parameter for these iteration macros to detect
> > overflow properly.
> > 
> > Please merge this through networking tree, as all the users
> > are in networking subsystem.
> 
> Series applied, thanks Cong.

Ugh, I don't even get the weekend to reply?

I think this is just a bad idea.  It'd be better to apply the conversion
patches to use XArray than fix up this crappy interface.  I didn't
reply before because I wanted to check those patches still apply and
post them as part of the response.  Now they're definitely broken and
need to be redone.