tty: Prevent ldisc drivers from re-using stale tty fields

[pandora-kernel.git] / drivers / tty / tty_ldisc.c

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index a69a755..82358c2 100644 (file)
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -36,6 +36,7 @@
 
 #include <linux/kmod.h>
 #include <linux/nsproxy.h>
+#include <linux/ratelimit.h>
 
 /*
  *     This guards the refcounted line discipline lists. The lock
@@ -423,6 +424,10 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush);
  *     they are not on hot paths so a little discipline won't do
  *     any harm.
  *
+ *     The line discipline-related tty_struct fields are reset to
+ *     prevent the ldisc driver from re-using stale information for
+ *     the new ldisc instance.
+ *
  *     Locking: takes termios_mutex
  */
 
@@ -431,6 +436,9 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
        mutex_lock(&tty->termios_mutex);
        tty->termios->c_line = num;
        mutex_unlock(&tty->termios_mutex);
+
+       tty->disc_data = NULL;
+       tty->receive_room = 0;
 }
 
 /**
@@ -837,7 +845,7 @@ void tty_ldisc_hangup(struct tty_struct *tty)
        tty_unlock();
        cancel_work_sync(&tty->buf.work);
        mutex_unlock(&tty->ldisc_mutex);
-
+retry:
        tty_lock();
        mutex_lock(&tty->ldisc_mutex);
 
@@ -846,7 +854,21 @@ void tty_ldisc_hangup(struct tty_struct *tty)
           it means auditing a lot of other paths so this is
           a FIXME */
        if (tty->ldisc) {       /* Not yet closed */
-               WARN_ON_ONCE(tty_ldisc_wait_idle(tty, 5 * HZ));
+               if (atomic_read(&tty->ldisc->users) != 1) {
+                       char cur_n[TASK_COMM_LEN], tty_n[64];
+                       long timeout = 3 * HZ;
+                       tty_unlock();
+
+                       while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
+                               timeout = MAX_SCHEDULE_TIMEOUT;
+                               printk_ratelimited(KERN_WARNING
+                                       "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
+                                       __func__, get_task_comm(cur_n, current),
+                                       tty_name(tty, tty_n));
+                       }
+                       mutex_unlock(&tty->ldisc_mutex);
+                       goto retry;
+               }
 
                if (reset == 0) {