linux-kernel - Re: [PATCH 1/1] Revert "perf: Remove the extra validity check on nr

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Date:	Mon, 2 Mar 2015 18:03:49 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	kan.liang@...el.com
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	xiakaixu@...wei.com, a.p.zijlstra@...llo.nl, ak@...ux.intel.com
Subject: Re: [PATCH 1/1] Revert "perf: Remove the extra validity check on
 nr_pages"

Em Mon, Mar 02, 2015 at 02:14:26AM -0500, kan.liang@...el.com escreveu:
> From: Kan Liang <kan.liang@...el.com>
> 
> This reverts commit 74390aa55678 ("perf: Remove the extra validity check
> on nr_pages")
> 
> nr_pages equals to number of pages - 1 in perf_mmap. So nr_pages = 0 is
> valide. So the nr_pages != 0 && !is_power_of_2(nr_pages) are all
> needed for checking. Otherwise, for example, perf test 6 failed.
> perf test 6
>  6: x86 rdpmc test                                         :Error:
> mmap() syscall returned with (Invalid argument)
>  FAILED!

Yeah, my bad, we need to revert this, its just on tip/perf/core, will
put the revert in my next pull request, thanks for spotting this!

- Arnaldo
 
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> ---
>  kernel/events/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 89f0f16..a83581c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -4423,7 +4423,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
>  	 * If we have rb pages ensure they're a power-of-two number, so we
>  	 * can do bitmasks instead of modulo.
>  	 */
> -	if (!is_power_of_2(nr_pages))
> +	if (nr_pages != 0 && !is_power_of_2(nr_pages))
>  		return -EINVAL;
>  
>  	if (vma_size != PAGE_SIZE * (1 + nr_pages))
> -- 
> 1.8.3.1
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