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SubjectRe: [PATCH 3/8] jump label: Fix error with preempt disable holding mutex
(2010/10/28 22:55), Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@redhat.com>
>
> 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.

Ah, right. Thank you for fixing it.

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

>
> Reported-by: Ingo Molnar <mingo@elte.hu>
> Cc: Jason Baron <jbaron@redhat.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> kernel/kprobes.c | 26 +++++++++++++-------------
> 1 files changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 9437e14..9737a76 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -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);
>


--
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com


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