linux-kernel - [PATCH v4 2/7] iommu: Lock group->mutex in iommu_deferred

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <9b9199e03c87c3cf8152cf93dc403a95c883811b.1756682135.git.nicolinc@nvidia.com>
Date: Sun, 31 Aug 2025 16:31:54 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <joro@...tes.org>, <jgg@...dia.com>, <bhelgaas@...gle.com>
CC: <suravee.suthikulpanit@....com>, <will@...nel.org>,
	<robin.murphy@....com>, <sven@...nel.org>, <j@...nau.net>,
	<alyssa@...enzweig.io>, <neal@...pa.dev>, <robin.clark@....qualcomm.com>,
	<m.szyprowski@...sung.com>, <krzk@...nel.org>, <alim.akhtar@...sung.com>,
	<dwmw2@...radead.org>, <baolu.lu@...ux.intel.com>, <kevin.tian@...el.com>,
	<yong.wu@...iatek.com>, <matthias.bgg@...il.com>,
	<angelogioacchino.delregno@...labora.com>, <tjeznach@...osinc.com>,
	<paul.walmsley@...ive.com>, <palmer@...belt.com>, <aou@...s.berkeley.edu>,
	<alex@...ti.fr>, <heiko@...ech.de>, <schnelle@...ux.ibm.com>,
	<mjrosato@...ux.ibm.com>, <gerald.schaefer@...ux.ibm.com>,
	<orsonzhai@...il.com>, <baolin.wang@...ux.alibaba.com>,
	<zhang.lyra@...il.com>, <wens@...e.org>, <jernej.skrabec@...il.com>,
	<samuel@...lland.org>, <jean-philippe@...aro.org>, <rafael@...nel.org>,
	<lenb@...nel.org>, <yi.l.liu@...el.com>, <cwabbott0@...il.com>,
	<quic_pbrahma@...cinc.com>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <asahi@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-arm-msm@...r.kernel.org>,
	<linux-samsung-soc@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>,
	<linux-riscv@...ts.infradead.org>, <linux-rockchip@...ts.infradead.org>,
	<linux-s390@...r.kernel.org>, <linux-sunxi@...ts.linux.dev>,
	<linux-tegra@...r.kernel.org>, <virtualization@...ts.linux.dev>,
	<linux-acpi@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<patches@...ts.linux.dev>, <vsethi@...dia.com>, <helgaas@...nel.org>,
	<etzhao1900@...il.com>
Subject: [PATCH v4 2/7] iommu: Lock group->mutex in iommu_deferred_attach()

The iommu_deferred_attach() function invokes __iommu_attach_device() while
not holding the group->mutex, like other __iommu_attach_device() callers.

Though there is no pratical bug being triggered so far, it would be better
to apply the same locking to this __iommu_attach_device(), since the IOMMU
drivers nowaday are more aware of the group->mutex -- some of them use the
iommu_group_mutex_assert() function that could be potentially in the path
of an attach_dev callback function invoked by the __iommu_attach_device().

The iommu_deferred_attach() will soon need to verify a new flag stored in
the struct group_device. To iterate the gdev list, the group->mutex should
be held for this matter too.

So, grab the mutex to guard __iommu_attach_device() like other callers.

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/iommu.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 060ebe330ee16..1e0116bce0762 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2144,10 +2144,17 @@ EXPORT_SYMBOL_GPL(iommu_attach_device);
 
 int iommu_deferred_attach(struct device *dev, struct iommu_domain *domain)
 {
-	if (dev->iommu && dev->iommu->attach_deferred)
-		return __iommu_attach_device(domain, dev);
+	/*
+	 * This is called on the dma mapping fast path so avoid locking. This is
+	 * racy, but we have an expectation that the driver will setup its DMAs
+	 * inside probe while being single threaded to avoid racing.
+	 */
+	if (!dev->iommu || !dev->iommu->attach_deferred)
+		return 0;
 
-	return 0;
+	guard(mutex)(&dev->iommu_group->mutex);
+
+	return __iommu_attach_device(domain, dev);
 }
 
 void iommu_detach_device(struct iommu_domain *domain, struct device *dev)
-- 
2.43.0