[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>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index 2a7c933651c7..f4330acead46 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -483,10 +483,14 @@ static void do_acct_process(struct file *file)
         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)));