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Subject: Re: [PATCH v3 00/34] iommu: Move iommu_group setup to IOMMU core code
To:     Qian Cai <cai@lca.pw>, Joerg Roedel <joro@8bytes.org>
Cc:     Heiko Stuebner <heiko@sntech.de>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        linux-tegra@vger.kernel.org,
        Thierry Reding <thierry.reding@gmail.com>,
        Daniel Drake <drake@endlessm.com>,
        Will Deacon <will@kernel.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        linux-samsung-soc@vger.kernel.org,
        iommu@lists.linux-foundation.org,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-rockchip@lists.infradead.org, Andy Gross <agross@kernel.org>,
        jonathan.derrick@intel.com, linux-s390@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, linux-mediatek@lists.infradead.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        virtualization@lists.linux-foundation.org,
        Gerald Schaefer <gerald.schaefer@de.ibm.com>,
        David Woodhouse <dwmw2@infradead.org>,
        linux-kernel@vger.kernel.org, Kukjin Kim <kgene@kernel.org>
References: <20200429133712.31431-1-joro@8bytes.org>
 <20200701004020.GA6221@lca.pw>
From:   Robin Murphy <robin.murphy@arm.com>
Message-ID: <9b0ef27a-f249-a90b-9899-e53b946f83cc@arm.com>
Date:   Wed, 1 Jul 2020 11:53:07 +0100
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On 2020-07-01 01:40, Qian Cai wrote:
> Looks like this patchset introduced an use-after-free on arm-smmu-v3.
> 
> Reproduced using mlx5,
> 
> # echo 1 > /sys/class/net/enp11s0f1np1/device/sriov_numvfs
> # echo 0 > /sys/class/net/enp11s0f1np1/device/sriov_numvfs
> 
> The .config,
> https://github.com/cailca/linux-mm/blob/master/arm64.config
> 
> Looking at the free stack,
> 
> iommu_release_device->iommu_group_remove_device
> 
> was introduced in 07/34 ("iommu: Add probe_device() and release_device()
> call-backs").

Right, iommu_group_remove_device can tear down the group and call 
->domain_free before the driver has any knowledge of the last device 
going away via the ->release_device call.

I guess the question is do we simply flip the call order in 
iommu_release_device() so drivers can easily clean up their internal 
per-device state first, or do we now want them to be robust against 
freeing domains with devices still nominally attached?

Robin.