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, 6 deletions

diff --git a/security/security.c b/security/security.c
index 32052f5c76b2..8c9fee59e60a 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1025,11 +1025,6 @@ int security_task_kill(struct task_struct *p, struct siginfo *info,
         return call_int_hook(task_kill, 0, p, info, sig, secid);
 }
 
-int security_task_wait(struct task_struct *p)
-{
-        return call_int_hook(task_wait, 0, p);
-}
-
 int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
                          unsigned long arg4, unsigned long arg5)
 {
@@ -1769,7 +1764,6 @@ struct security_hook_heads security_hook_heads = {
         .task_movememory =
                 LIST_HEAD_INIT(security_hook_heads.task_movememory),
         .task_kill =    LIST_HEAD_INIT(security_hook_heads.task_kill),
-        .task_wait =    LIST_HEAD_INIT(security_hook_heads.task_wait),
         .task_prctl =   LIST_HEAD_INIT(security_hook_heads.task_prctl),
         .task_to_inode =
                 LIST_HEAD_INIT(security_hook_heads.task_to_inode),