On Wed, Sep 7, 2022 at 3:50 PM Herbert Xu [off-list ref] wrote:

On Tue, Sep 06, 2022 at 04:11:58PM -0700, Eric Dumazet wrote:

quoted

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.