linux-kernel - Re: [PATCH] tracing: Fix unmapping loop in tracing_mark

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Date:	Mon, 09 Feb 2015 15:33:58 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Vikram Mulukutla <markivx@...eaurora.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>
CC:	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	Lime Yang <limey@...eaurora.org>
Subject: Re: [PATCH] tracing: Fix unmapping loop in tracing_mark_write

On 12/17/14 18:50, Vikram Mulukutla wrote:
> Commit 6edb2a8a385f0cdef51dae37ff23e74d76d8a6ce introduced
> an array map_pages that contains the addresses returned by
> kmap_atomic. However, when unmapping those pages, map_pages[0]
> is unmapped before map_pages[1], breaking the nesting requirement
> as specified in the documentation for kmap_atomic/kunmap_atomic.
>
> This was caught by the highmem debug code present in kunmap_atomic.
> Fix the loop to do the unmapping properly.
>
> Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>
> Reported-by: Lime Yang <limey@...eaurora.org>
> Signed-off-by: Vikram Mulukutla <markivx@...eaurora.org>
> ---

ping? What happened to this patch?

>  kernel/trace/trace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index ab76b7b..bceed34 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -4931,7 +4931,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
>  	*fpos += written;
>  
>   out_unlock:
> -	for (i = 0; i < nr_pages; i++){
> +	for (i = nr_pages - 1; i >= 0; i--) {
>  		kunmap_atomic(map_page[i]);
>  		put_page(pages[i]);
>  	}


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