Re: patch md-linear-fix-a-division-by-zero-bug-for-very-small-arrays.patch added to 2.6.27-stable tree

Hi

On Dienstag, 11. November 2008, [email]gregkh@suse.de[/email] wrote:[color=blue]
>
> This is a note to let you know that we have just queued up the patch titled
>
> Subject: md: linear: Fix a division by zero bug for very small arrays.
> Subject: md: linear: Fix a division by zero bug for very small arrays.
>
> to the 2.6.27-stable tree. Its filename is
>
> md-linear-fix-a-division-by-zero-bug-for-very-small-arrays.patch
>
> A git repo of this tree can be found at
> [url]http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary[/url]
>
>
> From [email]jejb@kernel.org[/email] Tue Nov 11 09:47:32 2008
> From: Andre Noll <maan@systemlinux.org>
> Date: Fri, 7 Nov 2008 00:07:46 GMT
> Subject: md: linear: Fix a division by zero bug for very small arrays.
> To: [email]stable@kernel.org[/email]
> Message-ID: <200811070007.mA707k6d006270@hera.kernel.org>
>
> From: Andre Noll <maan@systemlinux.org>
>
> commit f1cd14ae52985634d0389e934eba25b5ecf24565 upstream
>
> Date: Thu, 6 Nov 2008 19:41:24 +1100
> Subject: md: linear: Fix a division by zero bug for very small arrays.
>
> We currently oops with a divide error on starting a linear software
> raid array consisting of at least two very small (< 500K) devices.
>
> The bug is caused by the calculation of the hash table size which
> tries to compute sector_div(sz, base) with "base" being zero due to
> the small size of the component devices of the array.
>
> Fix this by requiring the hash spacing to be at least one which
> implies that also "base" is non-zero.
>
> This bug has existed since about 2.6.14.
>
> Signed-off-by: Andre Noll <maan@systemlinux.org>
> Signed-off-by: NeilBrown <neilb@suse.de>
> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
>
> ---
> drivers/md/linear.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> --- a/drivers/md/linear.c
> +++ b/drivers/md/linear.c
> @@ -157,6 +157,8 @@ static linear_conf_t *linear_conf(mddev_
>
> min_spacing = conf->array_sectors / 2;
> sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
> + if (min_sectors == 0)
> + min_sectors = 1;
>
> /* min_spacing is the minimum spacing that will fit the hash
> * table in one PAGE. This may be much smaller than needed.[/color]

drivers/md/linear.c: In function 'linear_conf':
drivers/md/linear.c:160: error: 'min_sectors' undeclared (first use in thisfunction)
drivers/md/linear.c:160: error: (Each undeclared identifier is reported only once
drivers/md/linear.c:160: error: for each function it appears in.)
make[5]: *** [drivers/md/linear.o] Error 1
make[4]: *** [drivers/md] Error 2
make[4]: *** Waiting for unfinished jobs....

This one obviously depends on:

commit 23242fbb470ff4c8c4d41f178832cf1929273d7d
Author: Andre Noll <maan@systemlinux.org>
Date: Mon Oct 13 11:55:12 2008 +1100

md: linear.c: Make two local variables sector-based.

which in turn depends on previous changes.

Regards
Stefan Lippers-Hollmann

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On Wed, November 12, 2008 9:28 am, Stefan Lippers-Hollmann wrote:[color=blue]
> Hi
>
> On Dienstag, 11. November 2008, [email]gregkh@suse.de[/email] wrote:[/color]
[color=blue][color=green]
>>
>> --- a/drivers/md/linear.c
>> +++ b/drivers/md/linear.c
>> @@ -157,6 +157,8 @@ static linear_conf_t *linear_conf(mddev_
>>
>> min_spacing = conf->array_sectors / 2;
>> sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
>> + if (min_sectors == 0)
>> + min_sectors = 1;
>>
>> /* min_spacing is the minimum spacing that will fit the hash
>> * table in one PAGE. This may be much smaller than needed.[/color]
>
> drivers/md/linear.c: In function 'linear_conf':
> drivers/md/linear.c:160: error: 'min_sectors' undeclared (first use in
> this function)
> drivers/md/linear.c:160: error: (Each undeclared identifier is reported
> only once
> drivers/md/linear.c:160: error: for each function it appears in.)
> make[5]: *** [drivers/md/linear.o] Error 1
> make[4]: *** [drivers/md] Error 2
> make[4]: *** Waiting for unfinished jobs....
>
> This one obviously depends on:
>
> commit 23242fbb470ff4c8c4d41f178832cf1929273d7d
> Author: Andre Noll <maan@systemlinux.org>
> Date: Mon Oct 13 11:55:12 2008 +1100
>
> md: linear.c: Make two local variables sector-based.
>
> which in turn depends on previous changes.[/color]

Yes, but only syntactically, not semantically.

In 2.6.27, it needs to be
if (min_spacing == 0)
min_spacing = 1;

The other previous patches don't need to be backported.

Thanks for reporting this.

NeilBrown

[color=blue]
>
> Regards
> Stefan Lippers-Hollmann
>[/color]

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On Wed, Nov 12, 2008 at 09:46:36AM +1100, NeilBrown wrote:[color=blue]
> On Wed, November 12, 2008 9:28 am, Stefan Lippers-Hollmann wrote:[color=green]
> > Hi
> >
> > On Dienstag, 11. November 2008, [email]gregkh@suse.de[/email] wrote:[/color]
>[color=green][color=darkred]
> >>
> >> --- a/drivers/md/linear.c
> >> +++ b/drivers/md/linear.c
> >> @@ -157,6 +157,8 @@ static linear_conf_t *linear_conf(mddev_
> >>
> >> min_spacing = conf->array_sectors / 2;
> >> sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
> >> + if (min_sectors == 0)
> >> + min_sectors = 1;
> >>
> >> /* min_spacing is the minimum spacing that will fit the hash
> >> * table in one PAGE. This may be much smaller than needed.[/color]
> >
> > drivers/md/linear.c: In function 'linear_conf':
> > drivers/md/linear.c:160: error: 'min_sectors' undeclared (first use in
> > this function)
> > drivers/md/linear.c:160: error: (Each undeclared identifier is reported
> > only once
> > drivers/md/linear.c:160: error: for each function it appears in.)
> > make[5]: *** [drivers/md/linear.o] Error 1
> > make[4]: *** [drivers/md] Error 2
> > make[4]: *** Waiting for unfinished jobs....
> >
> > This one obviously depends on:
> >
> > commit 23242fbb470ff4c8c4d41f178832cf1929273d7d
> > Author: Andre Noll <maan@systemlinux.org>
> > Date: Mon Oct 13 11:55:12 2008 +1100
> >
> > md: linear.c: Make two local variables sector-based.
> >
> > which in turn depends on previous changes.[/color]
>
> Yes, but only syntactically, not semantically.
>
> In 2.6.27, it needs to be
> if (min_spacing == 0)
> min_spacing = 1;[/color]

Thanks, I've adjusted the patch to look like this instead.

greg k-h
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