From: Baolu Lu <baolu.lu@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
David Woodhouse <dwmw2@infradead.org>,
Heiko Stuebner <heiko@sntech.de>,
iommu@lists.linux.dev, Jernej Skrabec <jernej.skrabec@gmail.com>,
Joerg Roedel <joro@8bytes.org>,
linux-arm-kernel@lists.infradead.org,
linux-rockchip@lists.infradead.org, linux-sunxi@lists.linux.dev,
Orson Zhai <orsonzhai@gmail.com>,
Robin Murphy <robin.murphy@arm.com>,
Samuel Holland <samuel@sholland.org>,
Chen-Yu Tsai <wens@csie.org>, Will Deacon <will@kernel.org>,
Chunyan Zhang <zhang.lyra@gmail.com>
Cc: baolu.lu@linux.intel.com, Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [PATCH 01/10] iommu: Remove useless group refcounting
Date: Thu, 20 Jul 2023 14:11:32 +0800 [thread overview]
Message-ID: <c7dd16ba-e4ab-b531-4a31-d310d1f943cc@linux.intel.com> (raw)
In-Reply-To: <1-v1-3c8177327a47+256-iommu_group_locking_jgg@nvidia.com>
On 2023/7/19 3:05, Jason Gunthorpe wrote:
> Several functions obtain the group reference and then release it before
> returning. This gives the impression that the refcount is protecting
> something for the duration of the function.
>
> In truth all of these functions are called in places that know a device
> driver is probed to the device and our locking rules already require
> that dev->iommu_group cannot change while a driver is attached to the
> struct device.
>
> If this was not the case then this code is already at risk of triggering
> UAF as it is racy if the dev->iommu_group is concurrently going to
> NULL/free. refcount debugging will throw a WARN if kobject_get() is
> called on a 0 refcount object to highlight the bug.
>
> Remove the confusing refcounting and leave behind a comment about the
> restriction.
>
> Signed-off-by: Jason Gunthorpe<jgg@nvidia.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Best regards,
baolu
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next prev parent reply other threads:[~2023-07-20 6:12 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-18 19:05 [PATCH 00/10] Refine the locking for dev->iommu_group Jason Gunthorpe
2023-07-18 19:05 ` [PATCH 01/10] iommu: Remove useless group refcounting Jason Gunthorpe
2023-07-20 6:11 ` Baolu Lu [this message]
2023-07-21 7:10 ` Tian, Kevin
2023-07-21 12:01 ` Jason Gunthorpe
2023-07-18 19:05 ` [PATCH 02/10] iommu: Add a lockdep assertion for remaining dev->iommu_group reads Jason Gunthorpe
2023-07-20 6:33 ` Baolu Lu
2023-07-18 19:05 ` [PATCH 03/10] iommu: Add generic_single_device_group() Jason Gunthorpe
2023-07-20 7:39 ` Baolu Lu
2023-07-20 12:04 ` Jason Gunthorpe
2023-07-20 14:01 ` Baolu Lu
2023-07-21 17:19 ` Jason Gunthorpe
2023-07-22 14:01 ` Baolu Lu
2023-07-21 7:17 ` Tian, Kevin
2023-07-22 14:02 ` Baolu Lu
2023-07-18 19:05 ` [PATCH 04/10] iommu/sun50i: Convert to generic_single_device_group() Jason Gunthorpe
2023-07-18 19:05 ` [PATCH 05/10] iommu/sprd: " Jason Gunthorpe
2023-07-18 19:05 ` [PATCH 06/10] iommu/rockchip: " Jason Gunthorpe
2023-07-18 19:05 ` [PATCH 07/10] iommu/ipmmu-vmsa: " Jason Gunthorpe
2023-07-21 7:20 ` Tian, Kevin
2023-07-21 12:04 ` Jason Gunthorpe
2023-07-18 19:05 ` [PATCH 08/10] iommu/omap: " Jason Gunthorpe
2023-07-18 19:05 ` [PATCH 09/10] iommu: Complete the locking for dev->iommu_group Jason Gunthorpe
2023-07-20 9:55 ` Baolu Lu
2023-07-18 19:05 ` [PATCH 10/10] iommu/intel: Fix missing locking for show_device_domain_translation() Jason Gunthorpe
2023-07-20 9:56 ` Baolu Lu
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