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Date: Sun, 5 Oct 2003 05:26:19 -0700 (PDT)
From: Don Lewis <truckman@FreeBSD.org>
To: bms@FreeBSD.org
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Subject: Re: cvs commit: src/sys/kern kern_sysctl.c
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On  5 Oct, Bruce M Simpson wrote:
> bms         2003/10/05 02:37:47 PDT
> 
>   FreeBSD src repository
> 
>   Modified files:
>     sys/kern             kern_sysctl.c 
>   Log:
>   Fix a security problem in sysctl() the long way round.
>   
>   Use pre-emption detection to avoid the need for wiring a userland buffer
>   when copying opaque data structures.

In the SMP case the data can change even without pre-emption.  There
have been a number of discussions (arch@, smp@, arch-handbook, etc.)
about adding a mutex parameter to the sysctl API.  Someone even
submitted a PR with a patch a few months ago (kern/54439), which I had
hoped to review but never found the time to.