linux-kernel - Re: [PATCH] kprobe: fix a memory leak in function pre_handler

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Date:	Mon, 9 Jan 2012 10:48:08 +0530
From:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	Jiang Liu <liuj97@...il.com>
Cc:	Jim Keniston <jkenisto@...ibm.com>, linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [PATCH] kprobe: fix a memory leak in function
	pre_handler_kretprobe()

On Sat, Jan 07, 2012 at 12:49:30AM +0800, Jiang Liu wrote:
> From: Jiang Liu<liuj97@...il.com>
>
> In function pre_handler_kretprobe(), the allocated kretprobe_instance object will
> be leaked if the entry_handler callback returns non-zero. This may cause all the
> preallocated kretprobe_instance objects exhausted. This issue could be reproduced
> by changing samples/kprobes/kretprobe_example.c to probe "mutex_unlock". And the
> fix is straight forward, just put the allocated kretprobe_instance object back
> onto the free_instances list.
>
> Signed-off-by: Jiang Liu<liuj97@...il.com>
> Cc: Hien Nguyen<hien@...ibm.com>
> Cc: Jim Keniston<jkenisto@...ibm.com>
> Cc: Prasanna S Panchamukhi<prasanna@...ibm.com>

Thanks for the patch.

Acked-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>

> ---
>  kprobes.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1660,8 +1660,12 @@
>                 ri->rp = rp;
>                 ri->task = current;
>
> -               if (rp->entry_handler&&  rp->entry_handler(ri, regs))
> +               if (rp->entry_handler&&  rp->entry_handler(ri, regs)) {
> +                       spin_lock_irqsave(&rp->lock, flags);
> +                       hlist_add_head(&ri->hlist,&rp->free_instances);
> +                       spin_unlock_irqrestore(&rp->lock, flags);
>                         return 0;
> +               }

Please fix up coding style issues and resend with acks from Jim and me.
Please also cc stable@...nel.org so this gets included in the earlier
kernels too.

Ananth

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