1 files changed, 11 insertions, 12 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index a0c1a29a507f..c7675c1bfdf2 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1381,7 +1381,7 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
 
         if (p->real_parent == group_leader) {
                 err = -EPERM;
-                if (p->signal->session != group_leader->signal->session)
+                if (process_session(p) != process_session(group_leader))
                         goto out;
                 err = -EACCES;
                 if (p->did_exec)
@@ -1397,16 +1397,13 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
                 goto out;
 
         if (pgid != pid) {
-                struct task_struct *p;
+                struct task_struct *g =
+                        find_task_by_pid_type(PIDTYPE_PGID, pgid);
 
-                do_each_task_pid(pgid, PIDTYPE_PGID, p) {
-                        if (p->signal->session == group_leader->signal->session)
-                                goto ok_pgid;
-                } while_each_task_pid(pgid, PIDTYPE_PGID, p);
-                goto out;
+                if (!g || process_session(g) != process_session(group_leader))
+                        goto out;
         }
 
-ok_pgid:
         err = security_task_setpgid(p, pgid);
         if (err)
                 goto out;
@@ -1459,7 +1456,7 @@ asmlinkage long sys_getpgrp(void)
 asmlinkage long sys_getsid(pid_t pid)
 {
         if (!pid)
-                return current->signal->session;
+                return process_session(current);
         else {
                 int retval;
                 struct task_struct *p;
@@ -1471,7 +1468,7 @@ asmlinkage long sys_getsid(pid_t pid)
                 if (p) {
                         retval = security_task_getsid(p);
                         if (!retval)
-                                retval = p->signal->session;
+                                retval = process_session(p);
                 }
                 read_unlock(&tasklist_lock);
                 return retval;
@@ -1484,7 +1481,6 @@ asmlinkage long sys_setsid(void)
         pid_t session;
         int err = -EPERM;
 
-        mutex_lock(&tty_mutex);
         write_lock_irq(&tasklist_lock);
 
         /* Fail if I am already a session leader */
@@ -1504,12 +1500,15 @@ asmlinkage long sys_setsid(void)
 
         group_leader->signal->leader = 1;
         __set_special_pids(session, session);
+
+        spin_lock(&group_leader->sighand->siglock);
         group_leader->signal->tty = NULL;
         group_leader->signal->tty_old_pgrp = 0;
+        spin_unlock(&group_leader->sighand->siglock);
+
         err = process_group(group_leader);
 out:
         write_unlock_irq(&tasklist_lock);
-        mutex_unlock(&tty_mutex);
         return err;
 }