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SubjectRe: [RFC][PATCH 11/11] security: AppArmor - Export namespace semaphore
On Wed, 2006-04-19 at 10:50 -0700, Tony Jones wrote:
> This patch exports the namespace_sem semaphore.
> The shared subtree patches which went into 2.6.15-rc1 replaced the old
> namespace semaphore which used to be per namespace (and visible) with a
> new single static semaphore.
> The reason for this change is that currently visibility of vfsmount information
> to the LSM hooks is fairly patchy. Either there is no passed parameter or
> it can be NULL. For the case of the former, several LSM hooks that we
> require to mediate have no vfsmount/nameidata passed. We previously (mis)used
> the visibility of the old per namespace semaphore to walk the processes
> namespace looking for vfsmounts with a root dentry matching the dentry we were
> trying to mediate.
> Clearly this is not viable long term strategy and changes working towards
> passing a vfsmount to all relevant LSM hooks would seem necessary (and also
> useful for other users of LSM). Alternative suggestions and ideas are welcomed.

The alternative I would recommend is to not use LSM. It isn't suitable
for your path-based approach. If your path-based approach is deemed
legitimate, then introduce new hooks at the proper point in processing
where the information you need is available.

Stephen Smalley
National Security Agency

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