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SubjectRe: PIDs limited to 15 significant bits
On Fri, Sep 29, 2000 at 03:57:10PM -0400, Albert D. Cahalan wrote:

> > The code is old.
> > There is very little reason for it, and we could change today.
> > My machines regularly see 6- or 7-digit PIDs.

> Oh, the horror!
>
> Consider, do you like to type "kill 1234567890" more than
> a simple "kill 1234"?

Hmm. I double click on the ps output and single click to paste.
The number of digits does not play a role.

> What do you think of "ps -efj" on a standard 80x24 screen?

I never give such commands, but just tried:

aeb 119876 1 426 236 0 23:32 tty1 00:00:00 xterm
aeb 119877 119876 119877 119877 0 23:32 pts/9 00:00:00 -bash
aeb 119884 119877 119884 119877 0 23:33 pts/9 00:00:00 ps -efj

as you see, the ps program here fails to align the columns,
but otherwise all is well.

> > [The patch is available. There are a few security advantages.
>
> There should not be any significant security advantages.
> One can easily wrap/predict in a 31-bit space.

There are a few weaknesses that can be exploited using a wraparound.
With 100 processes/sec that takes 497 days with a 32-bit pid
and 5 minutes with a 16-bit pid.

Andries
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