commit eb84a20e9e6b98dcb33023ad22241d79107a08a7
author Alan Cox <alan@lxorguk.ukuu.org.uk> Fri Sep 29 02:01:41 2006 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> Fri Sep 29 09:18:25 2006 -0700
tree 4971aef730cc3a1917463afe1dbb381dea664e99
parent 5f412b24240d92212e50ebbaff2dff20c9e6f3d0

[PATCH] audit/accounting: tty locking

Add tty locking around the audit and accounting code.

The whole current->signal-> locking is all deeply strange but it's for
someone else to sort out.  Add rather than replace the lock for acct.c

Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/acct.c

diff --git a/kernel/acct.c b/kernel/acct.c
index 2a7c933..f4330ac 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -483,10 +483,14 @@
 	ac.ac_ppid = current->parent->tgid;
 #endif
 
-	read_lock(&tasklist_lock);	/* pin current->signal */
+	mutex_lock(&tty_mutex);
+	/* FIXME: Whoever is responsible for current->signal locking needs
+	   to use the same locking all over the kernel and document it */
+	read_lock(&tasklist_lock);
 	ac.ac_tty = current->signal->tty ?
 		old_encode_dev(tty_devnum(current->signal->tty)) : 0;
 	read_unlock(&tasklist_lock);
+	mutex_unlock(&tty_mutex);
 
 	spin_lock_irq(&current->sighand->siglock);
 	ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));