zram: fix invalid memory references during disk write

[Greg KH]

On Mon, Jan 14, 2013 at 04:48:18PM -0800, Nitin Gupta wrote:
> On Mon, Jan 14, 2013 at 11:19 AM, Greg KH <gregkh at linuxfoundation.org> wrote:
> > On Wed, Dec 19, 2012 at 11:39:15AM -0600, Mitch Harder wrote:
> >> On Wed, Dec 19, 2012 at 11:21 AM, Nitin Gupta <ngupta at vflare.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 at linuxfoundation.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 at vger.kernel.org> # staging-next: 37b51fd: zram: factor-out
> >> >>>>>>>>>                               # zram_decompress_page() function
> >> >>>>>>>>> Signed-off-by: Nitin Gupta <ngupta at vflare.org>
> >> >>>>>>>>> Reported-by: Mihail Kasadjikov <hamer.mk at gmail.com>
> >> >>>>>>>>> Reported-by: Tomas M <tomas at slax.org>
> >> >>>>>>>>> Reviewed-by: Minchan Kim <minchan at kernel.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.
> >
> > Ok, I'm totally confused.
> >
> > Please, can someone tell me _exactly_ what commits they wish to see
> > applied to the 3.7-stable tree.
> >
> > thanks,
> >
> > greg k-h
> 
> These two needs to be applied to 3.7-stable:
> 
> 1) 37b51fd: "staging: zram: factor-out zram_decompress_page() function"
> 
> and then...
> 
> 2) 397c606: "staging: zram: fix invalid memory references during disk write"

Thanks, that makes sense.

But note, until today, I could not have done this at all, as the last
commit here was not in Linus's tree.  So I was right to be confused,
there was nothing I could do at the time.

Please be more careful in the future, developer's time is limited,
causing confusion doesn't help.

greg k-h