linux-kernel - Re: [PATCH 00/14] iommu: fix device leaks

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Message-ID: <20250930182158.GS2695987@ziepe.ca>
Date: Tue, 30 Sep 2025 15:21:58 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Johan Hovold <johan@...nel.org>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>, Sven Peter <sven@...nel.org>,
	Janne Grunau <j@...nau.net>,
	Rob Clark <robin.clark@....qualcomm.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Yong Wu <yong.wu@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Chen-Yu Tsai <wens@...e.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Krishna Reddy <vdumpa@...dia.com>, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/14] iommu: fix device leaks

On Thu, Sep 25, 2025 at 02:27:42PM +0200, Johan Hovold wrote:
> This series fixes device leaks in the iommu drivers, which pretty
> consistently failed to drop the reference taken by
> of_find_device_by_node() when looking up iommu platform devices.

Yes, they are mis-designed in many ways :\

IDK if it is worth fixing like this, or if more effort should be put
to make the drivers use of_xlate properly - the arm smmu drivers show
the only way to use it..

But if staying like this then maybe add a little helper?

void *iommu_xlate_to_iommu_drvdata(const struct of_phandle_args *args);

Put the whole racy of_find_device_by_node / put_device /
platform_get_drvdata sequence is in one tidy function.. With
documentation it is not safe don't use it in new code?

Jason