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Commit e4cc0a9c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

fix setsid() for sub-namespace /sbin/init 



sys_setsid() still deals with pid_t's from the global namespace. This means
that the "session > 1" check can't help for sub-namespace init, setsid() can't
succeed because copy_process(CLONE_NEWPID) populates PIDTYPE_PGID/SID links.

Remove the usage of task_struct->pid and convert the code to use "struct pid".
This also simplifies and speedups the code, saves one find_pid().

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: default avatarPavel Emelyanov <xemul@openvz.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4e021306

kernel/sys.c

+10 −12
Original line number Diff line number Diff line
@@ -1045,35 +1045,33 @@ asmlinkage long sys_getsid(pid_t pid) 
asmlinkage long sys_setsid(void)

{

	struct task_struct *group_leader = current->group_leader;

	pid_t session;

	struct pid *sid = task_pid(group_leader);

	pid_t session = pid_vnr(sid);

	int err = -EPERM;



	write_lock_irq(&tasklist_lock);



	/* Fail if I am already a session leader */

	if (group_leader->signal->leader)

		goto out;



	session = group_leader->pid;

	/* 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 id == 1 because kernel threads 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 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.

	 */

	if (session > 1 && find_task_by_pid_type_ns(PIDTYPE_PGID,

				session, &init_pid_ns))

	if (session != 1 && pid_task(sid, PIDTYPE_PGID))

		goto out;



	group_leader->signal->leader = 1;

	__set_special_pids(session, session);

	__set_special_pids(pid_nr(sid), pid_nr(sid));



	spin_lock(&group_leader->sighand->siglock);

	group_leader->signal->tty = NULL;

	spin_unlock(&group_leader->sighand->siglock);



	err = task_pgrp_vnr(group_leader);

	err = session;

out:

	write_unlock_irq(&tasklist_lock);

	return err;