Re: Detecting missing hook functions

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dwheelerat_private

I'm the poor soul who reported the complete system lockup running Mozilla -
Stephen did a great job in tracking down the problem.

Something needs to be done about this; this is an easy mistake to make, it's
easily missed, and it has dire consequences.

> 
> 
> Message: 4
> Date: Thu, 25 Oct 2001 13:22:01 -0400 (EDT)
> From: Stephen Smalley <sdsat_private>
> To: <linux-security-moduleat_private>
> Subject: Detecting missing hook functions
> 
> 
> At present, if you accidentally miss a hook function when writing your
> security module, you don't get any kind of warning unless it happens to
> be one of the top-level hooks (checked by security/security.c:verify).
> This happened to the SELinux security module.  Back at the beginning of
> August, a set of additional hooks were added to task_security_ops by
> Lachlan, and I missed the getscheduler hook when I updated the SELinux
> module.  We made three releases of the SELinux security module without
> noticing this problem, and only happened to find it after a user reported
> a complete system lockup upon running mozilla on the third release.  Even
> then, it wasn't easy to track down - we didn't get any kind of kernel
> Oops until we rolled forward to 2.4.13-pre6, just a complete lockup.
> 
> Although this was my mistake, it would be nice if the verify function
> would catch these kinds of mistakes.  But simply expanding the current set
> tests for each individual hook function pointer seems painful and may not
> be well-maintained as new hooks are added.  Is there a simpler way to
> validate the entire structure?
> 
> --
> Stephen D. Smalley, NAI Labs
> ssmalleyat_private

> 

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