netdev - Re: [PATCH v2 net] ipv4: update fib_info

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Date:   Mon, 17 Jan 2022 01:45:47 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        syzbot <syzkaller@...glegroups.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>
Subject: Re: [PATCH v2 net] ipv4: update fib_info_cnt under spinlock protection

On Mon, Jan 17, 2022 at 1:20 AM David Laight <David.Laight@...lab.com> wrote:

> This probably ought to be a stable candidate.
>
> If an increment is lost due to the unlocked inc/dec it is
> possible for the count to wrap to -1 if all fib are deleted.
> That will cause the table size to be doubled on every
> allocate (until the count goes +ve again).
>
> Losing a decrement is less of a problem.
> You'd need to lose a lot of them for any ill effect.
>

You are rephrasing the syzbot report, and the Fixes: tag I added in
the changelog.

hint: netdev maintainers handle the stable backports based on the
Fixes: tag, and their
own judgement.