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

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Date:	Wed, 19 Dec 2012 11:39:15 -0600
From:	Mitch Harder <mitch.harder@...ayonlinux.org>
To:	Nitin Gupta <ngupta@...are.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	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 Wed, Dec 19, 2012 at 11:21 AM, Nitin Gupta <ngupta@...are.org> wrote:
> 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?
>

Greg:

I think there is still some residual confusion from the mix of patches
sent out for this issue.

You appear to be saying that this patch as well as "37b51fd: zram:
factor-out  zram_decompress_page() function" have already been
applied.

But I do not see either patch in 3.7.0 or in your message for
"3.7.1-stable review"

I see the "37b51fd: zram: factor-out  zram_decompress_page() function"
patch in Linus' tree for 3.8_rc, but not the patch discussed in this
thread.
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