[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>

1 files changed, 6 insertions, 5 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index d8e49e659027..43e557211d8d 100644
--- 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;