diff options
Diffstat (limited to 'kernel/sys.c')
| -rw-r--r-- | kernel/sys.c | 38 |
1 files changed, 22 insertions, 16 deletions
diff --git a/kernel/sys.c b/kernel/sys.c index a0c1a29a507..6e2101dec0f 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -323,11 +323,18 @@ EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister); int blocking_notifier_call_chain(struct blocking_notifier_head *nh, unsigned long val, void *v) { - int ret; + int ret = NOTIFY_DONE; - down_read(&nh->rwsem); - ret = notifier_call_chain(&nh->head, val, v); - up_read(&nh->rwsem); + /* + * We check the head outside the lock, but if this access is + * racy then it does not matter what the result of the test + * is, we re-check the list after having taken the lock anyway: + */ + if (rcu_dereference(nh->head)) { + down_read(&nh->rwsem); + ret = notifier_call_chain(&nh->head, val, v); + up_read(&nh->rwsem); + } return ret; } @@ -1381,7 +1388,7 @@ 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 +1404,13 @@ 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 +1463,7 @@ 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 +1475,7 @@ 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 +1488,6 @@ 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 +1507,15 @@ 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; } |