Re: [PATCH 5.4 058/194] mtd: Fix gluebi NULL pointer dereference caused by ftl notifier

Re: [PATCH 5.4 058/194] mtd: Fix gluebi NULL pointer dereference caused by ftl notifier

[Martin Kepplinger-Novakovic]

Am Montag, dem 22.01.2024 um 15:56 -0800 schrieb Greg Kroah-Hartman:
> 5.4-stable review patch.  If anyone has any objections, please let me
> know.
> 
> ------------------
> 
> From: ZhaoLong Wang <wangzhaolong1@huawei.com>
> 
> [ Upstream commit a43bdc376deab5fff1ceb93dca55bcab8dbdc1d6 ]
> 
> If both ftl.ko and gluebi.ko are loaded, the notifier of ftl
> triggers NULL pointer dereference when trying to access
> ‘gluebi->desc’ in gluebi_read().
> 
> ubi_gluebi_init
>   ubi_register_volume_notifier
>     ubi_enumerate_volumes
>       ubi_notify_all
>         gluebi_notify    nb->notifier_call()
>           gluebi_create
>             mtd_device_register
>               mtd_device_parse_register
>                 add_mtd_device
>                   blktrans_notify_add   not->add()
>                     ftl_add_mtd         tr->add_mtd()
>                       scan_header
>                         mtd_read
>                           mtd_read_oob
>                             mtd_read_oob_std
>                               gluebi_read   mtd->read()
>                                 gluebi->desc - NULL
> 
> Detailed reproduction information available at the Link [1],
> 
> In the normal case, obtain gluebi->desc in the gluebi_get_device(),
> and access gluebi->desc in the gluebi_read(). However,
> gluebi_get_device() is not executed in advance in the
> ftl_add_mtd() process, which leads to NULL pointer dereference.
> 
> The solution for the gluebi module is to run jffs2 on the UBI
> volume without considering working with ftl or mtdblock [2].
> Therefore, this problem can be avoided by preventing gluebi from
> creating the mtdblock device after creating mtd partition of the
> type MTD_UBIVOLUME.
> 
> Fixes: 2ba3d76a1e29 ("UBI: make gluebi a separate module")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217992 [1]
> Link:
> https://lore.kernel.org/lkml/441107100.23734.1697904580252.JavaMail.zimbra@nod.at/
>  [2]
> Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>
> Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
> Acked-by: Richard Weinberger <richard@nod.at>
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Link:
> https://lore.kernel.org/linux-mtd/20231220024619.2138625-1-wangzhaolong1@huawei.com
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/mtd/mtd_blkdevs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
> index 0c05f77f9b21..dd0d0bf5f57f 100644
> --- a/drivers/mtd/mtd_blkdevs.c
> +++ b/drivers/mtd/mtd_blkdevs.c
> @@ -533,7 +533,7 @@ static void blktrans_notify_add(struct mtd_info
> *mtd)
>  {
>         struct mtd_blktrans_ops *tr;
>  
> -       if (mtd->type == MTD_ABSENT)
> +       if (mtd->type == MTD_ABSENT || mtd->type == MTD_UBIVOLUME)
>                 return;
>  
>         list_for_each_entry(tr, &blktrans_majors, list)
> @@ -576,7 +576,7 @@ int register_mtd_blktrans(struct mtd_blktrans_ops
> *tr)
>         list_add(&tr->list, &blktrans_majors);
>  
>         mtd_for_each_device(mtd)
> -               if (mtd->type != MTD_ABSENT)
> +               if (mtd->type != MTD_ABSENT && mtd->type !=
> MTD_UBIVOLUME)
>                         tr->add_mtd(tr, mtd);
>  
>         mutex_unlock(&mtd_table_mutex);

Hi Greg, hi patch-developers,

wait a second. this already went into v5.4.268 but still: Doesn't this
break userspace?

According to
https://lore.kernel.org/lkml/441107100.23734.1697904580252.JavaMail.zimbra@nod.at/
where this solution seems to come from, the behaviour changes: "no
mtdblock (hence, also no FTLs) on top of gluebi."

I fell accross this because of an out-of-tree module that does
sys_mount() an mtdblock, so I won't complain about my code specifically
:) But doesn't it break mounting, say, jffs2 inside an ubi via
mtdblock? If so, is this really something that you want to see
backported to old kernels?

Or differently put: Has this patch been picked up for old stable
kernels by scripts or by a human?

I just want to make sure, and who knows, it might help others too, who
would just do a (possibly dangerous?) revert in their trees.

thanks!
                          martin


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Re: [PATCH 5.4 058/194] mtd: Fix gluebi NULL pointer dereference caused by ftl notifier

[Zhihao Cheng]

在 2024/2/9 15:09, Martin Kepplinger-Novakovic 写道:
> Am Montag, dem 22.01.2024 um 15:56 -0800 schrieb Greg Kroah-Hartman:
>> 5.4-stable review patch.  If anyone has any objections, please let me
>> know.
>>
>> ------------------
>>
>> From: ZhaoLong Wang <wangzhaolong1@huawei.com>
>>
>> [ Upstream commit a43bdc376deab5fff1ceb93dca55bcab8dbdc1d6 ]
>>

[...]

>> diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
>> index 0c05f77f9b21..dd0d0bf5f57f 100644
>> --- a/drivers/mtd/mtd_blkdevs.c
>> +++ b/drivers/mtd/mtd_blkdevs.c
>> @@ -533,7 +533,7 @@ static void blktrans_notify_add(struct mtd_info
>> *mtd)
>>   {
>>          struct mtd_blktrans_ops *tr;
>>   
>> -       if (mtd->type == MTD_ABSENT)
>> +       if (mtd->type == MTD_ABSENT || mtd->type == MTD_UBIVOLUME)
>>                  return;
>>   
>>          list_for_each_entry(tr, &blktrans_majors, list)
>> @@ -576,7 +576,7 @@ int register_mtd_blktrans(struct mtd_blktrans_ops
>> *tr)
>>          list_add(&tr->list, &blktrans_majors);
>>   
>>          mtd_for_each_device(mtd)
>> -               if (mtd->type != MTD_ABSENT)
>> +               if (mtd->type != MTD_ABSENT && mtd->type !=
>> MTD_UBIVOLUME)
>>                          tr->add_mtd(tr, mtd);
>>   
>>          mutex_unlock(&mtd_table_mutex);
> 
> Hi Greg, hi patch-developers,
> 
> wait a second. this already went into v5.4.268 but still: Doesn't this
> break userspace?
> 
> According to
> https://lore.kernel.org/lkml/441107100.23734.1697904580252.JavaMail.zimbra@nod.at/
> where this solution seems to come from, the behaviour changes: "no
> mtdblock (hence, also no FTLs) on top of gluebi."
> 
> I fell accross this because of an out-of-tree module that does
> sys_mount() an mtdblock, so I won't complain about my code specifically
> :) But doesn't it break mounting, say, jffs2 inside an ubi via
> mtdblock? If so, is this really something that you want to see
> backported to old kernels?
> 
> Or differently put: Has this patch been picked up for old stable
> kernels by scripts or by a human?
> 
> I just want to make sure, and who knows, it might help others too, who
> would just do a (possibly dangerous?) revert in their trees.
> 

This change does affect the mounting(mtdblock based on gluebi) behavior 
in userspace. It was picked into stable versions because the fixed 
problem is serious and easy to be reproduced, I guess.
A temporary solution is that modify mounting source target in userspace, 
just replace mtdblock with mtd char device. For example, mount -t jffs2 
mtd0 /mnt

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Re: [PATCH 5.4 058/194] mtd: Fix gluebi NULL pointer dereference caused by ftl notifier

[Richard Weinberger]

----- Ursprüngliche Mail -----
> Von: "chengzhihao1" <chengzhihao1@huawei.com>
>> Hi Greg, hi patch-developers,
>> 
>> wait a second. this already went into v5.4.268 but still: Doesn't this
>> break userspace?
>> 
>> According to
>> https://lore.kernel.org/lkml/441107100.23734.1697904580252.JavaMail.zimbra@nod.at/
>> where this solution seems to come from, the behaviour changes: "no
>> mtdblock (hence, also no FTLs) on top of gluebi."
>> 
>> I fell accross this because of an out-of-tree module that does
>> sys_mount() an mtdblock, so I won't complain about my code specifically
>> :) But doesn't it break mounting, say, jffs2 inside an ubi via
>> mtdblock? If so, is this really something that you want to see
>> backported to old kernels?
>> 
>> Or differently put: Has this patch been picked up for old stable
>> kernels by scripts or by a human?
>> 
>> I just want to make sure, and who knows, it might help others too, who
>> would just do a (possibly dangerous?) revert in their trees.
>> 
> 
> This change does affect the mounting(mtdblock based on gluebi) behavior
> in userspace. It was picked into stable versions because the fixed
> problem is serious and easy to be reproduced, I guess.
> A temporary solution is that modify mounting source target in userspace,
> just replace mtdblock with mtd char device. For example, mount -t jffs2
> mtd0 /mnt

I don't think this needs backporting to stable. It's not serious because you
still need to be root to setup and trigger such a scenario.

Thanks,
//richard

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Re: [PATCH 5.4 058/194] mtd: Fix gluebi NULL pointer dereference caused by ftl notifier

[Zhihao Cheng]

在 2024/2/18 18:25, Richard Weinberger 写道:
> ----- Ursprüngliche Mail -----
>> Von: "chengzhihao1" <chengzhihao1@huawei.com>
>>> Hi Greg, hi patch-developers,
>>>
>>> wait a second. this already went into v5.4.268 but still: Doesn't this
>>> break userspace?
>>>
>>> According to
>>> https://lore.kernel.org/lkml/441107100.23734.1697904580252.JavaMail.zimbra@nod.at/
>>> where this solution seems to come from, the behaviour changes: "no
>>> mtdblock (hence, also no FTLs) on top of gluebi."
>>>
>>> I fell accross this because of an out-of-tree module that does
>>> sys_mount() an mtdblock, so I won't complain about my code specifically
>>> :) But doesn't it break mounting, say, jffs2 inside an ubi via
>>> mtdblock? If so, is this really something that you want to see
>>> backported to old kernels?
>>>
>>> Or differently put: Has this patch been picked up for old stable
>>> kernels by scripts or by a human?
>>>
>>> I just want to make sure, and who knows, it might help others too, who
>>> would just do a (possibly dangerous?) revert in their trees.
>>>
>>
>> This change does affect the mounting(mtdblock based on gluebi) behavior
>> in userspace. It was picked into stable versions because the fixed
>> problem is serious and easy to be reproduced, I guess.
>> A temporary solution is that modify mounting source target in userspace,
>> just replace mtdblock with mtd char device. For example, mount -t jffs2
>> mtd0 /mnt
> 
> I don't think this needs backporting to stable. It's not serious because you
> still need to be root to setup and trigger such a scenario.
> 


Yes. I feel okay to revert this patch on stable versions.

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