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audit: Call tty_audit_push_task() outside preempt disabled

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While auditing all tasklist_lock read_lock sites I stumbled over the
following call chain:

audit_prepare_user_tty()
  read_lock(&tasklist_lock);
  tty_audit_push_task();
     mutex_lock(&buf->mutex);

     --> buf->mutex is locked with preemption disabled.

Solve this by acquiring a reference to the task struct under
rcu_read_lock and call tty_audit_push_task outside of the preempt
disabled region.

Move all code which needs to be protected by sighand lock into
tty_audit_push_task() and use lock/unlock_sighand as we do not hold
tasklist_lock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Thomas Gleixner
2009-12-09 14:19:31 +00:00
committed by Al Viro
parent f7a998a949
commit 3c80fe4ac9
3 changed files with 42 additions and 30 deletions
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25
kernel/audit.c
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@ -467,23 +467,16 @@ static int audit_prepare_user_tty(pid_t pid, uid_t loginuid, u32 sessionid)
struct task_struct *tsk;
int err;
read_lock(&tasklist_lock);
rcu_read_lock();
tsk = find_task_by_vpid(pid);
err = -ESRCH;
if (!tsk)
goto out;
err = 0;
spin_lock_irq(&tsk->sighand->siglock);
if (!tsk->signal->audit_tty)
err = -EPERM;
spin_unlock_irq(&tsk->sighand->siglock);
if (err)
goto out;
tty_audit_push_task(tsk, loginuid, sessionid);
out:
read_unlock(&tasklist_lock);
if (!tsk) {
rcu_read_unlock();
return -ESRCH;
}
get_task_struct(tsk);
rcu_read_unlock();
err = tty_audit_push_task(tsk, loginuid, sessionid);
put_task_struct(tsk);
return err;
}