security,selinux,smack: kill security_task_wait hook

As reported by yangshukui, a permission denial from security_task_wait()
can lead to a soft lockup in zap_pid_ns_processes() since it only expects
sys_wait4() to return 0 or -ECHILD. Further, security_task_wait() can
in general lead to zombies; in the absence of some way to automatically
reparent a child process upon a denial, the hook is not useful.  Remove
the security hook and its implementations in SELinux and Smack.  Smack
already removed its check from its hook.

Reported-by: yangshukui <yangshukui@huawei.com>
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 0 insertions, 7 deletions

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 0dde95900196..6fe7a5cb0be1 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -666,11 +666,6 @@
  *	@sig contains the signal value.
  *	@secid contains the sid of the process where the signal originated
  *	Return 0 if permission is granted.
- * @task_wait:
- *	Check permission before allowing a process to reap a child process @p
- *	and collect its status information.
- *	@p contains the task_struct for process.
- *	Return 0 if permission is granted.
  * @task_prctl:
  *	Check permission before performing a process control operation on the
  *	current process.
@@ -1507,7 +1502,6 @@ union security_list_options {
 	int (*task_movememory)(struct task_struct *p);
 	int (*task_kill)(struct task_struct *p, struct siginfo *info,
 				int sig, u32 secid);
-	int (*task_wait)(struct task_struct *p);
 	int (*task_prctl)(int option, unsigned long arg2, unsigned long arg3,
 				unsigned long arg4, unsigned long arg5);
 	void (*task_to_inode)(struct task_struct *p, struct inode *inode);
@@ -1767,7 +1761,6 @@ struct security_hook_heads {
 	struct list_head task_getscheduler;
 	struct list_head task_movememory;
 	struct list_head task_kill;
-	struct list_head task_wait;
 	struct list_head task_prctl;
 	struct list_head task_to_inode;
 	struct list_head ipc_permission;