[PATCH][RESEND] disassociate_ctty SMP fix

[PATCH][RESEND] disassociate_ctty SMP fix

[Rik van Riel]

[resend #1]

Hi,

the following patch, against today's BK tree, fixes a small
SMP race in disassociate_ctty.  This function gets called
from do_exit, without the BKL held.

However, it sets the *tty variable before grabbing the bkl,
then makes decisions on what the variable was set to before
the lock was grabbed, despite the fact that another process
could modify its ->tty pointer in this same function.

please apply

Rik
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===== drivers/char/tty_io.c 1.50 vs edited =====
--- 1.50/drivers/char/tty_io.c	Sat Dec  7 16:23:16 2002
+++ edited/drivers/char/tty_io.c	Sat Jan 11 11:37:34 2003
@@ -577,7 +577,7 @@
  */
 void disassociate_ctty(int on_exit)
 {
-	struct tty_struct *tty = current->tty;
+	struct tty_struct *tty;
 	struct task_struct *p;
 	struct list_head *l;
 	struct pid *pid;
@@ -585,6 +585,7 @@

 	lock_kernel();

+	tty = current->tty;
 	if (tty) {
 		tty_pgrp = tty->pgrp;
 		if (on_exit && tty->driver.type != TTY_DRIVER_TYPE_PTY)