From: Greg KH <gregkh@linuxfoundation.org>
To: Olav Haugan <ohaugan@codeaurora.org>
Cc: ngupta@vflare.org, sjenning@linux.vnet.ibm.com,
linux-kernel@vger.kernel.org, minchan@kernel.org,
linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] staging: zsmalloc: Ensure handle is never 0 on success
Date: Tue, 5 Nov 2013 17:56:45 -0800 [thread overview]
Message-ID: <20131106015645.GA28769@kroah.com> (raw)
In-Reply-To: <1383699252-8898-1-git-send-email-ohaugan@codeaurora.org>
On Tue, Nov 05, 2013 at 04:54:12PM -0800, Olav Haugan wrote:
> zsmalloc encodes a handle using the page pfn and an object
> index. On some hardware platforms the pfn could be 0 and this
> causes the encoded handle to be 0 which is interpreted as an
> allocation failure.
What platforms specifically have this issue?
>
> To prevent this false error we ensure that the encoded handle
> will not be 0 when allocation succeeds.
>
> Change-Id: Ifff930dcf254915b497aec5cb36f152a5e5365d6
What is this? What can anyone do with it?
> Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
> ---
> drivers/staging/zsmalloc/zsmalloc-main.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
> index 523b937..0e32c0f 100644
> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
> @@ -441,7 +441,7 @@ static void *obj_location_to_handle(struct page *page, unsigned long obj_idx)
> }
>
> handle = page_to_pfn(page) << OBJ_INDEX_BITS;
> - handle |= (obj_idx & OBJ_INDEX_MASK);
> + handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);
>
> return (void *)handle;
> }
> @@ -451,7 +451,7 @@ static void obj_handle_to_location(unsigned long handle, struct page **page,
> unsigned long *obj_idx)
> {
> *page = pfn_to_page(handle >> OBJ_INDEX_BITS);
> - *obj_idx = handle & OBJ_INDEX_MASK;
> + *obj_idx = (handle & OBJ_INDEX_MASK) - 1;
> }
I need someone who knows how to test this code to ack it before I can
take it...
And I thought we were deleting zsmalloc anyway, why are you using this
code? Isn't it no longer needed anymore?
greg k-h
next prev parent reply other threads:[~2013-11-06 2:33 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-06 0:54 [PATCH] staging: zsmalloc: Ensure handle is never 0 on success Olav Haugan
2013-11-06 1:17 ` David Cohen
2013-11-06 20:56 ` Nitin Gupta
2013-11-06 23:46 ` Olav Haugan
2013-11-06 1:56 ` Greg KH [this message]
2013-11-06 21:09 ` Nitin Gupta
2013-11-06 22:10 ` Greg KH
2013-11-06 23:46 ` Nitin Gupta
2013-11-07 3:05 ` Greg KH
2013-11-07 0:00 ` Olav Haugan
2013-11-07 3:06 ` Greg KH
2013-11-07 22:57 ` Olav Haugan
2013-11-07 7:04 Minchan Kim
2013-11-07 17:06 ` Luigi Semenzato
2013-11-07 17:36 ` Luigi Semenzato
2013-11-08 2:02 ` Greg KH
2013-11-07 17:10 ` Rik van Riel
2013-11-08 10:44 ` Bob Liu
2013-11-12 15:41 ` Minchan Kim
2013-11-13 2:42 ` Greg KH
2013-11-13 6:24 ` Nitin Gupta
2013-11-14 4:00 ` Hugh Dickins
2013-11-14 16:21 ` Seth Jennings
2013-11-15 0:47 ` Bob Liu
2013-11-15 0:31 ` Minchan Kim
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