From: Ashish Mhetre <amhetre@nvidia.com>
Date: Tue, 10 Aug 2021 10:14:00 +0530
Subject: iommu: Fix race condition during default domain allocation
Git-commit: 211ff31b3d33b56aa12937e898c9280d07daf0d9
Patch-mainline: v5.15-rc1
References: bsc#1192202

When two devices with same SID are getting probed concurrently through
iommu_probe_device(), the iommu_domain sometimes is getting allocated more
than once as call to iommu_alloc_default_domain() is not protected for
concurrency. Furthermore, it leads to each device holding a different
iommu_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_alloc_default_domain() call with group->mutex
and let all devices with same SID share same iommu_domain.

Signed-off-by: Ashish Mhetre <amhetre@nvidia.com>
Link: https://lore.kernel.org/r/1628570641-9127-2-git-send-email-amhetre@nvidia.com
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/iommu.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -279,7 +279,9 @@ int iommu_probe_device(struct device *de
 	 * support default domains, so the return value is not yet
 	 * checked.
 	 */
+	mutex_lock(&group->mutex);
 	iommu_alloc_default_domain(group, dev);
+	mutex_unlock(&group->mutex);
 
 	if (group->default_domain) {
 		ret = __iommu_attach_device(group->default_domain, dev);