[PATCH] setpgid: should work for sub-threads

setsid() does not work unless the calling process is a
thread_group_leader().

'man setpgid' does not tell anything about that, so I consider this
behaviour is a bug.

Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index a80824f..caceabf 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -257,7 +257,7 @@ static inline void reparent_to_init(void)
 
 void __set_special_pids(pid_t session, pid_t pgrp)
 {
-       struct task_struct *curr = current;
+       struct task_struct *curr = current->group_leader;
 
        if (curr->signal->session != session) {
                detach_pid(curr, PIDTYPE_SID);

diff --git a/kernel/sys.c b/kernel/sys.c
index 43e5572..f497bf5 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1215,24 +1215,22 @@ asmlinkage long sys_getsid(pid_t pid)
 
 asmlinkage long sys_setsid(void)
 {
+       struct task_struct *group_leader = current->group_leader;
        struct pid *pid;
        int err = -EPERM;
 
-       if (!thread_group_leader(current))
-               return -EINVAL;
-
        down(&tty_sem);
        write_lock_irq(&tasklist_lock);
 
-       pid = find_pid(PIDTYPE_PGID, current->pid);
+       pid = find_pid(PIDTYPE_PGID, group_leader->pid);
        if (pid)
                goto out;
 
-       current->signal->leader = 1;
-       __set_special_pids(current->pid, current->pid);
-       current->signal->tty = NULL;
-       current->signal->tty_old_pgrp = 0;
-       err = process_group(current);
+       group_leader->signal->leader = 1;
+       __set_special_pids(group_leader->pid, group_leader->pid);
+       group_leader->signal->tty = NULL;
+       group_leader->signal->tty_old_pgrp = 0;
+       err = process_group(group_leader);
 out:
        write_unlock_irq(&tasklist_lock);
        up(&tty_sem);