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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Date:   Tue, 1 Sep 2020 18:35:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sean Young <sean@...s.org>
Cc:     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 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 :)

thanks,

greg k-h