linux-kernel - [PATCH 1/3] iommu/vt-d: Remove cache tags before disabling ATS

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Message-ID: <20241213011752.1177061-2-baolu.lu@linux.intel.com>
Date: Fri, 13 Dec 2024 09:17:50 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Joerg Roedel <joro@...tes.org>
Cc: Dan Carpenter <dan.carpenter@...aro.org>,
	Yi Liu <yi.l.liu@...el.com>,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] iommu/vt-d: Remove cache tags before disabling ATS

The current implementation removes cache tags after disabling ATS,
leading to potential memory leaks and kernel crashes. Specifically,
CACHE_TAG_DEVTLB type cache tags may still remain in the list even
after the domain is freed, causing a use-after-free condition.

This issue really shows up when multiple VFs from different PFs
passed through to a single user-space process via vfio-pci. In such
cases, the kernel may crash with kernel messages like:

 BUG: kernel NULL pointer dereference, address: 0000000000000014
 PGD 19036a067 P4D 1940a3067 PUD 136c9b067 PMD 0
 Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI
 CPU: 74 UID: 0 PID: 3183 Comm: testCli Not tainted 6.11.9 #2
 RIP: 0010:cache_tag_flush_range+0x9b/0x250
 Call Trace:
  <TASK>
  ? __die+0x1f/0x60
  ? page_fault_oops+0x163/0x590
  ? exc_page_fault+0x72/0x190
  ? asm_exc_page_fault+0x22/0x30
  ? cache_tag_flush_range+0x9b/0x250
  ? cache_tag_flush_range+0x5d/0x250
  intel_iommu_tlb_sync+0x29/0x40
  intel_iommu_unmap_pages+0xfe/0x160
  __iommu_unmap+0xd8/0x1a0
  vfio_unmap_unpin+0x182/0x340 [vfio_iommu_type1]
  vfio_remove_dma+0x2a/0xb0 [vfio_iommu_type1]
  vfio_iommu_type1_ioctl+0xafa/0x18e0 [vfio_iommu_type1]

Move cache_tag_unassign_domain() before iommu_disable_pci_caps() to fix
it.

Fixes: 3b1d9e2b2d68 ("iommu/vt-d: Add cache tag assignment interface")
Cc: stable@...r.kernel.org
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Link: https://lore.kernel.org/r/20241129020506.576413-1-baolu.lu@linux.intel.com
---
 drivers/iommu/intel/iommu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 7d0acb74d5a5..79e0da9eb626 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3220,6 +3220,9 @@ void device_block_translation(struct device *dev)
 	struct intel_iommu *iommu = info->iommu;
 	unsigned long flags;
 
+	if (info->domain)
+		cache_tag_unassign_domain(info->domain, dev, IOMMU_NO_PASID);
+
 	iommu_disable_pci_caps(info);
 	if (!dev_is_real_dma_subdevice(dev)) {
 		if (sm_supported(iommu))
@@ -3236,7 +3239,6 @@ void device_block_translation(struct device *dev)
 	list_del(&info->link);
 	spin_unlock_irqrestore(&info->domain->lock, flags);
 
-	cache_tag_unassign_domain(info->domain, dev, IOMMU_NO_PASID);
 	domain_detach_iommu(info->domain, iommu);
 	info->domain = NULL;
 }
-- 
2.43.0