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SubjectRe: [PATCH 4/9] jump label: Fix deadlock b/w jump_label_mutex vs. text_mutex
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On Fri, 2010-10-15 at 22:55 +0200, Peter Zijlstra wrote:
> On Fri, 2010-10-15 at 16:09 -0400, Steven Rostedt wrote:
> > +void jump_label_lock(void)
> > +{
> > + mutex_lock(&jump_label_mutex);
> > +}
> > +
>
> > +++ b/kernel/kprobes.c
> > @@ -1145,13 +1145,16 @@ int __kprobes register_kprobe(struct kprobe *p)
> > return ret;
> >
> > preempt_disable();
> > + jump_label_lock();
>
> How exactly does that work?
>

This patch should fix it (compiled tested only). If all agree, I'll add
it to the series.

-- Steve

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d45d72e..0dbd328 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1144,17 +1144,13 @@ int __kprobes register_kprobe(struct kprobe *p)
if (ret)
return ret;

- preempt_disable();
jump_label_lock();
+ preempt_disable();
if (!kernel_text_address((unsigned long) p->addr) ||
in_kprobes_functions((unsigned long) p->addr) ||
ftrace_text_reserved(p->addr, p->addr) ||
- jump_label_text_reserved(p->addr, p->addr)) {
- preempt_enable();
- jump_label_unlock();
- return -EINVAL;
- }
- jump_label_unlock();
+ jump_label_text_reserved(p->addr, p->addr))
+ goto fail_with_jump_label;

/* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
p->flags &= KPROBE_FLAG_DISABLED;
@@ -1168,10 +1164,9 @@ int __kprobes register_kprobe(struct kprobe *p)
* We must hold a refcount of the probed module while updating
* its code to prohibit unexpected unloading.
*/
- if (unlikely(!try_module_get(probed_mod))) {
- preempt_enable();
- return -EINVAL;
- }
+ if (unlikely(!try_module_get(probed_mod)))
+ goto fail_with_jump_label;
+
/*
* If the module freed .init.text, we couldn't insert
* kprobes in there.
@@ -1179,11 +1174,11 @@ int __kprobes register_kprobe(struct kprobe *p)
if (within_module_init((unsigned long)p->addr, probed_mod) &&
probed_mod->state != MODULE_STATE_COMING) {
module_put(probed_mod);
- preempt_enable();
- return -EINVAL;
+ goto fail_with_jump_label;
}
}
preempt_enable();
+ jump_label_unlock();

p->nmissed = 0;
INIT_LIST_HEAD(&p->list);
@@ -1225,6 +1220,11 @@ out:
module_put(probed_mod);

return ret;
+
+fail_with_jump_label:
+ preempt_enable();
+ jump_label_unlock();
+ return -EINVAL;
}
EXPORT_SYMBOL_GPL(register_kprobe);




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