Re: [PATCH 1/2] namespaces: give each namespace a serial number
On 14/05/02, Serge E. Hallyn wrote:
Quoting Richard Guy Briggs (rgb(a)redhat.com):
Most of this looks reasonable, but I'm curious about something,
> +/**
> + * ns_serial - compute a serial number for the namespace
> + *
> + * Compute a serial number for the namespace to uniquely identify it in
> + * audit records.
> + */
> +unsigned int ns_serial(void)
> +{
> + static DEFINE_SPINLOCK(serial_lock);
> + static unsigned int serial = 4; /* reserved for IPC, UTS, user, PID */
> +
> + unsigned long flags;
> + unsigned int ret;
> +
> + spin_lock_irqsave(&serial_lock, flags);
> + do {
> + ret = ++serial;
> + } while (unlikely(!ret));
Why exactly are you doing this? Surely if serial is going to
wrap around we've got a bigger problem than just wanting go
bump one more time?
Thanks for catching this.
The code was templated off audit_serial() which tries to solve a
different problem and rolling it is much more likely. I hadn't noticed
that rollover protection. However, I *had* thought of making it a long
(which would be the same size on 32-bit arches, but larger on 64-bit)
since a 64-bit system is more likely to roll it out of sheer speed and
resource availability. But perhaps a long long would be safer.
> + spin_unlock_irqrestore(&serial_lock, flags);
> +
> + return ret;
> +}
- RGB
--
Richard Guy Briggs <rbriggs(a)redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
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