netdev - RE: UBSAN reports issue in ip_idents

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB01049DD@AcuExch.aculab.com>
Date:   Tue, 20 Sep 2016 13:36:19 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Eric Dumazet' <eric.dumazet@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: UBSAN reports issue in ip_idents_reserve

From: Eric Dumazet
> Sent: 20 September 2016 14:29
...
> > [   47.565420] -2117905507 + -695755206 cannot be represented in type 'int'
...
> I do not think we have to worry here.
>
> These is best effort, and unfortunately atomic_t are int.

Not until we compile on a cpu where int arithmetic doesn't wrap.

While I expect that various other parts of the kernel (and userspace)
wouldn't like such cpu, they do exist.

	David