Commit de31c3ca authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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jump label: Fix error with preempt disable holding mutex 



Kprobes and jump label were having a race between mutexes that
was fixed by reordering the jump label. But this reordering
moved the jump label mutex into a preempt disable location.

This patch does a little fiddling to move the grabbing of
the jump label mutex from inside the preempt disable section
and still keep the order correct between the mutex and the
kprobes lock.

Reported-by: default avatarIngo Molnar <mingo@elte.hu>
Acked-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Jason Baron <jbaron@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 91bad2f8

kernel/kprobes.c

+13 −13
Original line number Diff line number Diff line
@@ -1145,17 +1145,13 @@ 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;
@@ -1169,10 +1165,9 @@ 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.
@@ -1180,11 +1175,11 @@ 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);
@@ -1226,6 +1221,11 @@ 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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