tty: Add a kref count
Introduce a kref to the tty structure and use it to protect the tty->signal
tty references. For now we don't introduce it for anything else.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/fork.c b/kernel/fork.c
index 7ce2ebe..30de644 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -802,6 +802,7 @@
sig->leader = 0; /* session leadership doesn't inherit */
sig->tty_old_pgrp = NULL;
+ sig->tty = NULL;
sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
sig->gtime = cputime_zero;
@@ -838,6 +839,7 @@
void __cleanup_signal(struct signal_struct *sig)
{
exit_thread_group_keys(sig);
+ tty_kref_put(sig->tty);
kmem_cache_free(signal_cachep, sig);
}
@@ -1227,7 +1229,8 @@
p->nsproxy->pid_ns->child_reaper = p;
p->signal->leader_pid = pid;
- p->signal->tty = current->signal->tty;
+ tty_kref_put(p->signal->tty);
+ p->signal->tty = tty_kref_get(current->signal->tty);
set_task_pgrp(p, task_pgrp_nr(current));
set_task_session(p, task_session_nr(current));
attach_pid(p, PIDTYPE_PGID, task_pgrp(current));