linux-kernel - Re: zram: fix invalid memory references during disk write

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Message-ID: <50D1F799.4060800@vflare.org>
Date:	Wed, 19 Dec 2012 09:21:29 -0800
From:	Nitin Gupta <ngupta@...are.org>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Jerome Marchand <jmarchan@...hat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org, Minchan Kim <minchan.kim@...il.com>,
	Linux Driver Project <devel@...uxdriverproject.org>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: zram: fix invalid memory references during disk write

On 12/19/2012 08:17 AM, Greg KH wrote:
> On Wed, Dec 19, 2012 at 07:53:36AM -0800, Nitin Gupta wrote:
>> On 12/19/2012 07:08 AM, Greg KH wrote:
>>> On Tue, Dec 18, 2012 at 11:21:28PM -0800, Nitin Gupta wrote:
>>>> On 12/18/2012 07:49 PM, Greg KH wrote:
>>>>> On Tue, Dec 18, 2012 at 01:12:05PM -0800, Nitin Gupta wrote:
>>>>>> On Tue, Dec 11, 2012 at 10:27 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
>>>>>>> On Thu, Nov 29, 2012 at 10:45:09PM -0800, Nitin Gupta wrote:
>>>>>>>> Fixes a bug introduced by commit c8f2f0db1 ("zram: Fix handling
>>>>>>>> of incompressible pages") which caused invalid memory references
>>>>>>>> during disk write. Invalid references could occur in two cases:
>>>>>>>>  - Incoming data expands on compression: In this case, reference was
>>>>>>>> made to kunmap()'ed bio page.
>>>>>>>>  - Partial (non PAGE_SIZE) write with incompressible data: In this
>>>>>>>> case, reference was made to a kfree()'ed buffer.
>>>>>>>>
>>>>>>>> Fixes bug 50081:
>>>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=50081
>>>>>>>>
>>>>>>>> Upstream commit ID: c8f2f0d: zram: Fix handling of incompressible pages
>>>>>>>> Apply to versions: 3.6.5, 3.6.6, 3.6.7, 3.6.8
>>>>>>>>
>>>>>>>> Cc: <stable@...r.kernel.org> # staging-next: 37b51fd: zram: factor-out
>>>>>>>>                               # zram_decompress_page() function
>>>>>>>> Signed-off-by: Nitin Gupta <ngupta@...are.org>
>>>>>>>> Reported-by: Mihail Kasadjikov <hamer.mk@...il.com>
>>>>>>>> Reported-by: Tomas M <tomas@...x.org>
>>>>>>>> Reviewed-by: Minchan Kim <minchan@...nel.org>
>>>>>>>> ---
>>>>>>>>  drivers/staging/zram/zram_drv.c |   39 ++++++++++++++++++++++++---------------
>>>>>>>>  1 file changed, 24 insertions(+), 15 deletions(-)
>>>>>>>
>>>>>>> This patch fails to apply to 3.6.10:
>>>>>>>
>>>>>>> patching file drivers/staging/zram/zram_drv.c
>>>>>>> Hunk #1 succeeded at 282 (offset 17 lines).
>>>>>>> Hunk #2 FAILED at 286.
>>>>>>> Hunk #3 succeeded at 319 (offset 17 lines).
>>>>>>> Hunk #4 succeeded at 340 (offset 17 lines).
>>>>>>> Hunk #5 succeeded at 353 (offset 17 lines).
>>>>>>> Hunk #6 succeeded at 368 (offset 17 lines).
>>>>>>> Hunk #7 succeeded at 385 (offset 17 lines).
>>>>>>> 1 out of 7 hunks FAILED -- saving rejects to file drivers/staging/zram/zram_drv.c.rej
>>>>>>>
>>>>>>> Please redo this patch and resend it if you wish for it to be applied to
>>>>>>> the 3.6-stable tree.
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> Please apply this patch to stable tree asap.
>>>>>
>>>>> 3.6 is now end-of-life, there will not be any more releases for that
>>>>> kernel series anymore, sorry.
>>>>>
>>>>
>>>> Then please apply to 3.7.
>>>
>>> That is impossible to do so, for the obvious reason.
>>>
>>
>> I meant to include it in whatever 3.7.x is released in future. Or put it
>> in staging, so it may eventually make it to mainline (by 3.8?).
> 
> {sigh}
> 
> Please think for a moment for how it would be impossible for me to add
> this patch to either the 3.7-stable tree, or the 3.8 tree, _again_.
>  

I'm simply not getting it, I'm sorry, I must be missing something
obvious -- what's really the problem with this: "whenever 3.8 is
released, sometime in the future, just make sure that this fix is
included in it" ?  Also, what's stopping it from staging, at least?

Nitin

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