From: Krishna Reddy <vdumpa@nvidia.com>
Date: Tue, 10 Aug 2021 10:14:01 +0530
Subject: iommu/arm-smmu: Fix race condition during iommu_group creation
Git-commit: b1a1347912a742a4e1fcdc9df6302dd9dd2c3405
Patch-mainline: v5.15-rc1
References: bsc#1192202

When two devices with same SID are getting probed concurrently through
iommu_probe_device(), the iommu_group sometimes is getting allocated more
than once as call to arm_smmu_device_group() is not protected for
concurrency. Furthermore, it leads to each device holding a different
iommu_group and domain pointer, separate IOVA space and only one of the
devices' domain is used for translations from IOMMU. This causes accesses
from other device to fault or see incorrect translations.
Fix this by protecting iommu_group allocation from concurrency in
arm_smmu_device_group().

Signed-off-by: Krishna Reddy <vdumpa@nvidia.com>
Signed-off-by: Ashish Mhetre <amhetre@nvidia.com>
Link: https://lore.kernel.org/r/1628570641-9127-3-git-send-email-amhetre@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1477,6 +1477,7 @@ static struct iommu_group *arm_smmu_devi
 	struct iommu_group *group = NULL;
 	int i, idx;
 
+	mutex_lock(&smmu->stream_map_mutex);
 	for_each_cfg_sme(cfg, fwspec, i, idx) {
 		if (group && smmu->s2crs[idx].group &&
 		    group != smmu->s2crs[idx].group)
@@ -1485,8 +1486,10 @@ static struct iommu_group *arm_smmu_devi
 		group = smmu->s2crs[idx].group;
 	}
 
-	if (group)
+	if (group) {
+		mutex_unlock(&smmu->stream_map_mutex);
 		return iommu_group_ref_get(group);
+	}
 
 	if (dev_is_pci(dev))
 		group = pci_device_group(dev);
@@ -1500,6 +1503,7 @@ static struct iommu_group *arm_smmu_devi
 		for_each_cfg_sme(cfg, fwspec, i, idx)
 			smmu->s2crs[idx].group = group;
 
+	mutex_unlock(&smmu->stream_map_mutex);
 	return group;
 }