Possible system call interface for LSM

lachlanat_private

There was some minor discussion recently about modules
needing to modify the system call table to create module
specific system calls.  It prompted me to investigate a
fixed system call for LSM that will multiplex the variety
of system calls required for each different security
scheme.  I've attached a patch of the proposed idea for
people to comment on.

The basis of the patch is to create a new system call
(sys_security) that accepts generic arguments (much like
ioctl) and performs the copy_from_user() and
copy_to_user() so the module doesn't have to worry about
it.  This method requires that the application (or an
associated library) know the format of the data that the
module is expecting.  For that reason, it could be
problematic if library A executed the system call of
module B.  I've added a module id field to the
security_ops structure that is set by the module when
loaded and is checked against the module id provided by
the application (or library) when the system call is
executed.

I'd appreciate any thoughts on this approach.

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Lachlan McIlroy                    Phone: +61 3 9596 4155
Trusted Linux                        Fax: +61 3 9596 2960
Adacel Technologies Ltd                    www.adacel.com