Re: [PATCH v8 08/26] tcp: authopt: Disable via sysctl by default

[Eric Dumazet]

On Wed, Sep 7, 2022 at 3:50 PM Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Tue, Sep 06, 2022 at 04:11:58PM -0700, Eric Dumazet wrote:
> >
> > WRITE_ONCE(sysctl_tcp_authopt, val),  or even better:
> >
> > if (val)
> >      cmpxchg(&sysctl_tcp_authopt, 0, val);
>
> What's the point of the cmpxchg? Since you're simply trying to prevent
> sysctl_tcp_authopt from going back to zero, then the if clause
> by itself is enough:
>
>         if (val)
>                 WRITE_ONCE(sysctl_tcp_authopt, val);
>

Ack.

Original patch was doing something racy, I have not though about the
most efficient way to deal with it.