From: "yukuai (C)" <yukuai3@huawei.com>
To: Robin Murphy <robin.murphy@arm.com>, <joro@8bytes.org>,
<heiko@sntech.de>, <jeffy.chen@rock-chips.com>
Cc: linux-rockchip@lists.infradead.org,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, yi.zhang@huawei.com
Subject: Re: [PATCH] iommu/rockchip: check return value of of_find_device_by_node() in rk_iommu_of_xlate()
Date: Fri, 30 Oct 2020 09:27:23 +0800 [thread overview]
Message-ID: <e3805bee-347a-1e66-b2ca-48f06df6f702@huawei.com> (raw)
In-Reply-To: <d5442e6b-2a6b-a8f9-2056-2c0c81e88a01@arm.com>
On 2020/10/29 21:51, Robin Murphy wrote:
> On 2020-10-29 13:19, yukuai (C) wrote:
>>
>> On 2020/10/29 18:08, Robin Murphy wrote:
>>> On 2020-10-29 09:22, Yu Kuai wrote:
>>>> If of_find_device_by_node() failed in rk_iommu_of_xlate(), null pointer
>>>> dereference will be triggered. Thus return error code if
>>>> of_find_device_by_node() failed.
>>>
>>> How can that happen? (Given that ".suppress_bind_attrs = true")
>>>
>>> Robin.
>>
>> I'm not sure if that could happen...
>>
>> My thought is that it's better to do such checking to aviod any possible
>> problem.
>
> ->of_xlate() is only invoked on the specific set of ops returned by
> iommu_ops_from_fwnode(). In turn, iommu_ops_from_fwnode() will only
> return those ops if the driver has successfully probed and called
> iommu_register_device() with the relevant DT node. For the driver to
> have been able to probe at all, a platform device associated with that
> DT node must have been created, and therefore of_find_device_by_node()
> cannot fail.
>
> If there ever were some problem serious enough to break that fundamental
> assumption, then I *want* these drivers to crash right here, with a nice
> clear stack trace to start debugging from. So no, I firmly disagree that
> adding redundant code, which will never do anything except attempt to
> paper over catastrophic memory corruption, is "better". Sorry :)
>
Sounds reasonable, thanks for your explanation
Yu Kuai
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prev parent reply other threads:[~2020-10-30 1:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-29 9:22 [PATCH] iommu/rockchip: check return value of of_find_device_by_node() in rk_iommu_of_xlate() Yu Kuai
2020-10-29 10:08 ` Robin Murphy
2020-10-29 13:19 ` yukuai (C)
2020-10-29 13:51 ` Robin Murphy
2020-10-30 1:27 ` yukuai (C) [this message]
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