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

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Message-ID: <912b7429-c294-418e-2082-ab269382f1f0@huawei.com>
Date: Sun, 18 Feb 2024 19:48:06 +0800
From: Zhihao Cheng <chengzhihao1@...wei.com>
To: Richard Weinberger <richard@....at>
CC: Martin Kepplinger-Novakovic <martink@...teo.de>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, stable <stable@...r.kernel.org>,
	<patches@...ts.linux.dev>, ZhaoLong Wang <wangzhaolong1@...wei.com>, Miquel
 Raynal <miquel.raynal@...tlin.com>, Sasha Levin <sashal@...nel.org>,
	linux-mtd <linux-mtd@...ts.infradead.org>, Vignesh Raghavendra
	<vigneshr@...com>, dpervushin <dpervushin@...eddedalley.com>, Artem
 Bityutskiy <Artem.Bityutskiy@...ia.com>, linux-kernel
	<linux-kernel@...r.kernel.org>, yi zhang <yi.zhang@...wei.com>, yangerkun
	<yangerkun@...wei.com>, Henri Roosen <Henri.Roosen@...zinger.com>, Melchior
 Franz <Melchior.Franz@...zinger.com>
Subject: Re: [PATCH 5.4 058/194] mtd: Fix gluebi NULL pointer dereference
 caused by ftl notifier

在 2024/2/18 18:25, Richard Weinberger 写道:
> ----- Ursprüngliche Mail -----
>> Von: "chengzhihao1" <chengzhihao1@...wei.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.