Hi Eric,
Here's another approach Mikey and I were discussing. We allocate the
tsk->audit_context as before, but we avoid setting the TIF_SYSCALL_AUDIT until
the first rule gets added.
We could look at clearing the flag when the rules go back to zero, but this
simple patch covers the most common case I think.
Anton
---
Index: powerpc.git/kernel/auditfilter.c
===================================================================
--- powerpc.git.orig/kernel/auditfilter.c 2010-08-26 08:04:19.998892577
+1000
+++ powerpc.git/kernel/auditfilter.c 2010-08-26 08:04:30.290374256 +1000
@@ -859,6 +859,21 @@ out:
static u64 prio_low = ~0ULL/2;
static u64 prio_high = ~0ULL/2 - 1;
+#ifdef CONFIG_AUDITSYSCALL
+static void enable_syscall_auditing(void)
+{
+ unsigned long flags;
+ struct task_struct *g, *t;
+
+ read_lock_irqsave(&tasklist_lock, flags);
+ do_each_thread(g, t) {
+ if (t->audit_context)
+ set_tsk_thread_flag(t, TIF_SYSCALL_AUDIT);
+ } while_each_thread(g, t);
+ read_unlock_irqrestore(&tasklist_lock, flags);
+}
+#endif
+
/* Add rule to given filterlist if not a duplicate. */
static inline int audit_add_rule(struct audit_entry *entry)
{
@@ -922,9 +937,14 @@ static inline int audit_add_rule(struct
list_add_tail_rcu(&entry->list, list);
}
#ifdef CONFIG_AUDITSYSCALL
- if (!dont_count)
+ if (!dont_count) {
audit_n_rules++;
+ /* Did we add our first rule? */
+ if (audit_n_rules == 1)
+ enable_syscall_auditing();
+ }
+
if (!audit_match_signal(entry))
audit_signals++;
#endif
Index: powerpc.git/kernel/auditsc.c
===================================================================
--- powerpc.git.orig/kernel/auditsc.c 2010-08-26 08:04:19.998892577 +1000
+++ powerpc.git/kernel/auditsc.c 2010-08-26 08:04:30.390388654 +1000
@@ -886,7 +886,10 @@ int audit_alloc(struct task_struct *tsk)
context->filterkey = key;
tsk->audit_context = context;
- set_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
+
+ /* We postpone setting the thread flag until we add the first rule */
+ if (audit_n_rules != 0)
+ set_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
return 0;
}
--
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