Re: [PATCH 08/28] SECURITY: Allow kernel services to override LSM settings for task actions [try #2]

[David Howells]

Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:

> Yes, but we're talking about writing the configuration information
> to the kernel, not actually making any access checks with it. I
> think. What I think we're talking about (and please correct me David
> if I've stepped into the wrong theatre) is getting the magic
> secctx that cachefiles will use instead of the secctx that the task
> would have otherwise. I don't think we're talking about recomputing
> it on every access, I think David is looking for the blunderbuss
> secctx that he can use any time he needs one.

Indeed.

The way I do it is:

 (1) The daemon opens /dev/cachefiles to being an instance of a cache.

 (2) The daemon negotiates a security context for the module to use.

 (3) The security context is place in a task_security structure.

 (4) This task_security struct is attached temporarily to task->act_as each
     time any task attempts to access the cache through the module.

 (5) The task_security struct is discarded when the file descriptor that was
     created in (1) is closed and the cache is withdrawn at the same time.

David
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