linux-kernel - Re: [PATCH 4.19 016/125] media: pci: ttpci: av7110: fix possible buffer overflow caused by bad DMA value in debiirq()

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Message-ID: <5c177bce-c7f8-6938-45a9-820d7d32e2e0@tsinghua.edu.cn>
Date:   Wed, 2 Sep 2020 09:23:41 +0800
From:   Jia-Ju Bai <baijiaju@...nghua.edu.cn>
To:     Pavel Machek <pavel@...x.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Sean Young <sean@...s.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Jia-Ju Bai <baijiaju@...nghua.edu.cn>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 016/125] media: pci: ttpci: av7110: fix possible
 buffer overflow caused by bad DMA value in debiirq()



On 2020/9/2 5:16, Pavel Machek wrote:
> On Tue 2020-09-01 18:35:23, Greg Kroah-Hartman wrote:
>> On Tue, Sep 01, 2020 at 05:25:12PM +0100, Sean Young wrote:
>>> Greg,
>>>
>>> On Tue, Sep 01, 2020 at 05:09:31PM +0200, Greg Kroah-Hartman wrote:
>>>> From: Jia-Ju Bai <baijiaju@...nghua.edu.cn>
>>>>
>>>> [ Upstream commit 6499a0db9b0f1e903d52f8244eacc1d4be00eea2 ]
>>>>
>>>> The value av7110->debi_virt is stored in DMA memory, and it is assigned
>>>> to data, and thus data[0] can be modified at any time by malicious
>>>> hardware. In this case, "if (data[0] < 2)" can be passed, but then
>>>> data[0] can be changed into a large number, which may cause buffer
>>>> overflow when the code "av7110->ci_slot[data[0]]" is used.
>>>>
>>>> To fix this possible bug, data[0] is assigned to a local variable, which
>>>> replaces the use of data[0].
>>> See the discussion here:
>>>
>>> https://lkml.org/lkml/2020/8/31/479
>>>
>>> It does not seem worthwhile merging to the stable trees.
>> It doesn't hurt either :)
> Update stable kernel rules.
>
> If "patch does not match description and is pretty obviously useless"
> but "does not hurt" is acceptable for stable tree, people should know.
>
> You are pushing known junk into stable. Stop that.

Sorry for my useless patch...

Recently I submitted a new patch wiith READ_ONCE() to fix the problem 
that Pavel said:
https://lkml.org/lkml/2020/8/30/67

If you think this new patch is still useless, reverting the code is fine 
to me.


Best wishes,
Jia-Ju Bai