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

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Date:	Wed, 11 Jan 2012 21:42:33 +0530
From:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	Jiang Liu <liuj97@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S . Miller" <davem@...emloft.net>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Jun Ma <harry.majun@...wei.com>, stable@...r.kernel.org,
	Jiang Liu <jiang.liu@...wei.com>
Subject: Re: [PATCH] kprobes: fix a memory leak in function
	pre_handler_kretprobe()

On Wed, Jan 11, 2012 at 11:21:51PM +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 <jiang.liu@...wei.com>
> Acked-by: Jim Keniston <jkenisto@...ibm.com>
> Acked-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>

Thank you Jiang. I think the correct ID for stable is now
stable@...r.kernel.org.

> ---
>  kernel/kprobes.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index e5d8464..2423295 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1673,8 +1673,12 @@ static int __kprobes pre_handler_kretprobe(struct kprobe *p,
>  		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;
> +		}
> 
>  		arch_prepare_kretprobe(ri, regs);
> 
> -- 
> 1.7.5.4

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