linux-kernel - Re: [PATCH] uprobes: Fix utask->depth accounting in handle

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Date:	Thu, 12 Sep 2013 12:19:00 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, anton@...hat.com,
	Hemant Kumar Shaw <hkshaw@...ux.vnet.ibm.com>,
	masami.hiramatsu.pt@...achi.com,
	Mikhail Kulemin <Mikhail.Kulemin@...ibm.com>,
	systemtap@...rceware.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uprobes: Fix utask->depth accounting in
 handle_trampoline()

* Oleg Nesterov <oleg@...hat.com> [2013-09-11 17:47:26]:

> Currently utask->depth is simply the number of allocated/pending
> return_instance's in uprobe_task->return_instances list.
> 
> handle_trampoline() should decrement this counter every time we
> handle/free an instance, but due to typo it does this only if
> ->chained == T. This means that in the likely case this counter
> is never decremented and the probed task can't report more than
> MAX_URETPROBE_DEPTH events.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> Reported-by: Mikhail Kulemin <Mikhail.Kulemin@...ibm.com>
> Reported-by: Hemant Kumar Shaw <hkshaw@...ux.vnet.ibm.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

Mikhail Kulemin has verified that this fix works for him.

> ---
>  kernel/events/uprobes.c |    4 +---
>  1 files changed, 1 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index f356974..ad8e1bd 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1682,12 +1682,10 @@ static bool handle_trampoline(struct pt_regs *regs)
>  		tmp = ri;
>  		ri = ri->next;
>  		kfree(tmp);
> +		utask->depth--;
> 
>  		if (!chained)
>  			break;
> -
> -		utask->depth--;
> -
>  		BUG_ON(!ri);
>  	}
> 
> -- 
> 1.5.5.1
> 
> 

-- 
Thanks and Regards
Srikar Dronamraju

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