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

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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: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2008-02-08 04:19:09 -08:00 • committed by Linus Torvalds
parent 4e021306cf
commit e4cc0a9c87
1 changed files with 10 additions and 12 deletions
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22
kernel/sys.c
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@ -1045,35 +1045,33 @@ asmlinkage long sys_getsid(pid_t pid)
asmlinkage long sys_setsid(void) asmlinkage long sys_setsid(void)
{ {
struct task_struct *group_leader = current->group_leader; 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; int err = -EPERM;
write_lock_irq(&tasklist_lock); write_lock_irq(&tasklist_lock);
/* Fail if I am already a session leader */ /* Fail if I am already a session leader */
if (group_leader->signal->leader) if (group_leader->signal->leader)
goto out; goto out;
session = group_leader->pid; /* Fail if a process group id already exists that equals the proposed
/* Fail if a process group id already exists that equals the * session id.
* proposed session id.
* *
* Don't check if session id == 1 because kernel threads use this * Don't check if session == 1 because kernel threads and CLONE_NEWPID
* session id and so the check will always fail and make it so * tasks use this session id and so the check will always fail and make
* init cannot successfully call setsid. * it so init cannot successfully call setsid.
*/ */
if (session > 1 && find_task_by_pid_type_ns(PIDTYPE_PGID, if (session != 1 && pid_task(sid, PIDTYPE_PGID))
session, &init_pid_ns))
goto out; goto out;
group_leader->signal->leader = 1; 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); spin_lock(&group_leader->sighand->siglock);
group_leader->signal->tty = NULL; group_leader->signal->tty = NULL;
spin_unlock(&group_leader->sighand->siglock); spin_unlock(&group_leader->sighand->siglock);
err = task_pgrp_vnr(group_leader); err = session;
out: out:
write_unlock_irq(&tasklist_lock); write_unlock_irq(&tasklist_lock);
return err; return err;