[PATCH] setpgid: should work for sub-threads

setpgid(0, pgid) or setpgid(forked_child_pid, pgid) 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: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Oren Laadan <orenl@cs.columbia.edu>
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/sys.c b/kernel/sys.c
index d8e49e6..43e5572 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1090,10 +1090,11 @@ asmlinkage long sys_times(struct tms __user * tbuf)
 asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 {
        struct task_struct *p;
+       struct task_struct *group_leader = current->group_leader;
        int err = -EINVAL;
 
        if (!pid)
-               pid = current->pid;
+               pid = group_leader->pid;
        if (!pgid)
                pgid = pid;
        if (pgid < 0)
@@ -1113,16 +1114,16 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
        if (!thread_group_leader(p))
                goto out;
 
-       if (p->parent == current || p->real_parent == current) {
+       if (p->parent == current || p->real_parent == group_leader) {
                err = -EPERM;
-               if (p->signal->session != current->signal->session)
+               if (p->signal->session != group_leader->signal->session)
                        goto out;
                err = -EACCES;
                if (p->did_exec)
                        goto out;
        } else {
                err = -ESRCH;
-               if (p != current)
+               if (p != group_leader)
                        goto out;
        }
 
@@ -1134,7 +1135,7 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
                struct task_struct *p;
 
                do_each_task_pid(pgid, PIDTYPE_PGID, p) {
-                       if (p->signal->session == current->signal->session)
+                       if (p->signal->session == group_leader->signal->session)
                                goto ok_pgid;
                } while_each_task_pid(pgid, PIDTYPE_PGID, p);
                goto out;