linux-kernel - Re: [PATCH 1/3] ARM: perf: Check that current->mm is alive before getting user callchain

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Date:	Thu, 3 Jul 2014 18:53:07 +0100
From:	Will Deacon <will.deacon@....com>
To:	Jean Pihet <jean.pihet@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Sneha Priya <sneha.cse@...mail.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [PATCH 1/3] ARM: perf: Check that current->mm is alive before
 getting user callchain

On Fri, Jun 27, 2014 at 03:57:45PM +0100, Jean Pihet wrote:
> An event may occur when an mm is already released.
> 
> As per commit 20afc60f892d285fde179ead4b24e6a7938c2f1b
>  'x86, perf: Check that current->mm is alive before getting user callchain'
> 
> Signed-off-by: Jean Pihet <jean.pihet@...aro.org>
> Cc: Will Deacon <will.deacon@....com>
> ---

Acked-by: Will Deacon <will.deacon@....com>

>  arch/arm/kernel/perf_event.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
> index 4238bcb..6493c4c 100644
> --- a/arch/arm/kernel/perf_event.c
> +++ b/arch/arm/kernel/perf_event.c
> @@ -590,6 +590,10 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
>  	}
>  
>  	perf_callchain_store(entry, regs->ARM_pc);
> +
> +	if (!current->mm)
> +		return;
> +
>  	tail = (struct frame_tail __user *)regs->ARM_fp - 1;
>  
>  	while ((entry->nr < PERF_MAX_STACK_DEPTH) &&
> -- 
> 1.8.1.2
> 
> 
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