selinux: Use task_alloc hook rather than task_create hook
This patch is a preparation for getting rid of task_create hook because task_alloc hook which can do what task_create hook can do was revived. Creating a new thread is unlikely prohibited by security policy, for fork()/execve()/exit() is fundamental of how processes are managed in Unix. If a program is known to create a new thread, it is likely that permission to create a new thread is given to that program. Therefore, a situation where security_task_create() returns an error is likely that the program was exploited and lost control. Even if SELinux failed to check permission to create a thread at security_task_create(), SELinux can later check it at security_task_alloc(). Since the new thread is not yet visible from the rest of the system, nobody can do bad things using the new thread. What we waste will be limited to some initialization steps such as dup_task_struct(), copy_creds() and audit_alloc() in copy_process(). We can tolerate these overhead for unlikely situation. Therefore, this patch changes SELinux to use task_alloc hook rather than task_create hook so that we can remove task_create hook. Signed-off-by:Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by:
Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by:
Paul Moore <paul@paul-moore.com>
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