start the global /sbin/init with 0,0 special pids (430c6231) · Commits · 戴 / test

As Eric pointed out, there is no problem with init starting with sid == pgid == 0, and this was historical linux behavior changed in 2.6.18. Remove kernel_init()->__set_special_pids(), this is unneeded and complicates the rules for sys_setsid(). This change and the previous change in daemonize() mean that /sbin/init does not need the special "session != 1" hack in sys_setsid() any longer. We can't remove this check yet, we should cleanup copy_process(CLONE_NEWPID) first, so update the comment only. Signed-off-by:

Oleg Nesterov <oleg@tv-sign.ru> Acked-by:

"Eric W. Biederman" <ebiederm@xmission.com> Cc: Pavel Emelyanov <xemul@openvz.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

init/main.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -833,7 +833,6 @@ static int __init kernel_init(void * unused)
		*/
		init_pid_ns.child_reaper = current;

		__set_special_pids(task_pid(current));
		cad_pid = task_pid(current);

		smp_prepare_cpus(setup_max_cpus);

kernel/sys.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -1054,12 +1054,11 @@ asmlinkage long sys_setsid(void)
		if (group_leader->signal->leader)
		goto out;

		/* Fail if a process group id already exists that equals the proposed
		* session id.
		/* Fail if a process group id already exists that equals the
		* proposed session id.
		*
		* Don't check if session == 1 because kernel threads and CLONE_NEWPID
		* tasks use this session id and so the check will always fail and make
		* it so init cannot successfully call setsid.
		* Don't check if session == 1, clone(CLONE_NEWPID) creates
		* this group/session beforehand.
		*/
		if (session != 1 && pid_task(sid, PIDTYPE_PGID))
		goto out;

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