From 6347e90091041e34bea625370794c92f4ce71228 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 20 Jun 2012 12:53:03 -0700 Subject: [PATCH] pidns: guarantee that the pidns init will be the last pidns process reaped Today we have a twofold bug. Sometimes release_task on pid == 1 in a pid namespace can run before other processes in a pid namespace have had release task called. With the result that pid_ns_release_proc can be called before the last proc_flus_task() is done using upid->ns->proc_mnt, resulting in the use of a stale pointer. This same set of circumstances can lead to waitpid(...) returning for a processes started with clone(CLONE_NEWPID) before the every process in the pid namespace has actually exited. To fix this modify zap_pid_ns_processess wait until all other processes in the pid namespace have exited, even EXIT_DEAD zombies. The delay_group_leader and related tests ensure that the thread gruop leader will be the last thread of a process group to be reaped, or to become EXIT_DEAD and self reap. With the change to zap_pid_ns_processes we get the guarantee that pid == 1 in a pid namespace will be the last task that release_task is called on. With pid == 1 being the last task to pass through release_task pid_ns_release_proc can no longer be called too early nor can wait return before all of the EXIT_DEAD tasks in a pid namespace have exited. Signed-off-by: Eric W. Biederman Signed-off-by: Oleg Nesterov Cc: Louis Rilling Cc: Mike Galbraith Acked-by: Pavel Emelyanov Tested-by: Andrew Wagin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-format-patch failed