Re: [PATCH] kprobes: Sanitize struct kretprobe_instance allocations

[Masami Hiramatsu <mhiramat@redhat.com>]

Ananth N Mavinakayanahalli wrote:
> From: Ananth N Mavinakayanahalli<ananth@in.ibm.com>
>
> For as long as kretprobes have existed, we've allocated NR_CPUS
> instances of kretprobe_instance structures. With the default value of
> CONFIG_NR_CPUS increasing on certain architectures, we are potentially
> wasting kernel memory.
>
> See http://sourceware.org/bugzilla/show_bug.cgi?id=10839#c3 for more
> details.
>
> Use a saner num_possible_cpus() instead of NR_CPUS for allocation.
>
> Signed-off-by: Ananth N Mavinakayanahalli<ananth@in.ibm.com>

Acked-by: Masami Hiramatsu <mhiramat@redhat.com>

Thanks!

> ---
>   kernel/kprobes.c |    4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> Index: linux-2.6.32-rc5/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.32-rc5.orig/kernel/kprobes.c
> +++ linux-2.6.32-rc5/kernel/kprobes.c
> @@ -1014,9 +1014,9 @@ int __kprobes register_kretprobe(struct
>   	/* Pre-allocate memory for max kretprobe instances */
>   	if (rp->maxactive<= 0) {
>   #ifdef CONFIG_PREEMPT
> -		rp->maxactive = max(10, 2 * NR_CPUS);
> +		rp->maxactive = max(10, 2 * num_possible_cpus());
>   #else
> -		rp->maxactive = NR_CPUS;
> +		rp->maxactive = num_possible_cpus();
>   #endif
>   	}
>   	spin_lock_init(&rp->lock);

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com