linux-kernel - Re: [PATCH] iommu: Avoid more races around device probe

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Message-ID: <20231124153520.GA558245@nvidia.com>
Date:   Fri, 24 Nov 2023 11:35:20 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     joro@...tes.org, will@...nel.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        rafael@...nel.org, lenb@...nel.org, lpieralisi@...nel.org,
        andre.draszik@...aro.org, quic_zhenhuah@...cinc.com
Subject: Re: [PATCH] iommu: Avoid more races around device probe

On Wed, Nov 15, 2023 at 06:25:44PM +0000, Robin Murphy wrote:
> It turns out there are more subtle races beyond just the main part of
> __iommu_probe_device() itself running in parallel - the dev_iommu_free()
> on the way out of an unsuccessful probe can still manage to trip up
> concurrent accesses to a device's fwspec. Thus, extend the scope of
> iommu_probe_device_lock() to also serialise fwspec creation and initial
> retrieval.
> 
> Reported-by: Zhenhua Huang <quic_zhenhuah@...cinc.com>
> Link: https://lore.kernel.org/linux-iommu/e2e20e1c-6450-4ac5-9804-b0000acdf7de@quicinc.com/

Apparently this is "Closes:" nowadays

> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index f17a1113f3d6..e0c962648dde 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -485,11 +485,12 @@ static void iommu_deinit_device(struct device *dev)
>  	dev_iommu_free(dev);
>  }
>  
> +DEFINE_MUTEX(iommu_probe_device_lock);
> +

Please put this at the top of the file with the other declarations, I
will rebase the lockdep annotations from the other series

Thanks,
Jason