linux-kernel - [PATCH 5.4 106/123] iommu/vt-d: Fix RCU-list bugs in intel_iommu

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Message-Id: <20200317103318.386788238@linuxfoundation.org>
Date:   Tue, 17 Mar 2020 11:55:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Qian Cai <cai@....pw>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>
Subject: [PATCH 5.4 106/123] iommu/vt-d: Fix RCU-list bugs in intel_iommu_init()

From: Qian Cai <cai@....pw>

commit 2d48ea0efb8887ebba3e3720bb5b738aced4e574 upstream.

There are several places traverse RCU-list without holding any lock in
intel_iommu_init(). Fix them by acquiring dmar_global_lock.

 WARNING: suspicious RCU usage
 -----------------------------
 drivers/iommu/intel-iommu.c:5216 RCU-list traversed in non-reader section!!

 other info that might help us debug this:

 rcu_scheduler_active = 2, debug_locks = 1
 no locks held by swapper/0/1.

 Call Trace:
  dump_stack+0xa0/0xea
  lockdep_rcu_suspicious+0x102/0x10b
  intel_iommu_init+0x947/0xb13
  pci_iommu_init+0x26/0x62
  do_one_initcall+0xfe/0x500
  kernel_init_freeable+0x45a/0x4f8
  kernel_init+0x11/0x139
  ret_from_fork+0x3a/0x50
 DMAR: Intel(R) Virtualization Technology for Directed I/O

Fixes: d8190dc63886 ("iommu/vt-d: Enable DMA remapping after rmrr mapped")
Signed-off-by: Qian Cai <cai@....pw>
Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/iommu/intel-iommu.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -5024,6 +5024,7 @@ int __init intel_iommu_init(void)
 
 	init_iommu_pm_ops();
 
+	down_read(&dmar_global_lock);
 	for_each_active_iommu(iommu, drhd) {
 		iommu_device_sysfs_add(&iommu->iommu, NULL,
 				       intel_iommu_groups,
@@ -5031,6 +5032,7 @@ int __init intel_iommu_init(void)
 		iommu_device_set_ops(&iommu->iommu, &intel_iommu_ops);
 		iommu_device_register(&iommu->iommu);
 	}
+	up_read(&dmar_global_lock);
 
 	bus_set_iommu(&pci_bus_type, &intel_iommu_ops);
 	if (si_domain && !hw_pass_through)
@@ -5041,7 +5043,6 @@ int __init intel_iommu_init(void)
 	down_read(&dmar_global_lock);
 	if (probe_acpi_namespace_devices())
 		pr_warn("ACPI name space devices didn't probe correctly\n");
-	up_read(&dmar_global_lock);
 
 	/* Finally, we enable the DMA remapping hardware. */
 	for_each_iommu(iommu, drhd) {
@@ -5050,6 +5051,8 @@ int __init intel_iommu_init(void)
 
 		iommu_disable_protect_mem_regions(iommu);
 	}
+	up_read(&dmar_global_lock);
+
 	pr_info("Intel(R) Virtualization Technology for Directed I/O\n");
 
 	intel_iommu_enabled = 1;