Linux Virtualization - Apr 2020 - [PATCH AUTOSEL 5.5 45/75] iommu/virtio: Fix freeing of incomplete domains

From: Jean-Philippe Brucker <jean-philippe at linaro.org>

[ Upstream commit 7062af3ed2ba451029e3733d9f677c68f5ea9e77 ]

Calling viommu_domain_free() on a domain that hasn't been finalised (not
attached to any device, for example) can currently cause an Oops,
because we attempt to call ida_free() on ID 0, which may either be
unallocated or used by another domain.

Only initialise the vdomain->viommu pointer, which denotes a finalised
domain, at the end of a successful viommu_domain_finalise().

Fixes: edcd69ab9a32 ("iommu: Add virtio-iommu driver")
Reported-by: Eric Auger <eric.auger at redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
Reviewed-by: Robin Murphy <robin.murphy at arm.com>
Link: https://lore.kernel.org/r/20200326093558.2641019-3-jean-philippe at
linaro.org
Signed-off-by: Joerg Roedel <jroedel at suse.de>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/iommu/virtio-iommu.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 315c7cc4f99d8..779a6025b5962 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -613,18 +613,20 @@ static int viommu_domain_finalise(struct viommu_dev
*viommu,
 	int ret;
 	struct viommu_domain *vdomain = to_viommu_domain(domain);
 
-	vdomain->viommu		= viommu;
-	vdomain->map_flags	= viommu->map_flags;
+	ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
+			      viommu->last_domain, GFP_KERNEL);
+	if (ret < 0)
+		return ret;
+
+	vdomain->id		= (unsigned int)ret;
 
 	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
 	domain->geometry	= viommu->geometry;
 
-	ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
-			      viommu->last_domain, GFP_KERNEL);
-	if (ret >= 0)
-		vdomain->id = (unsigned int)ret;
+	vdomain->map_flags	= viommu->map_flags;
+	vdomain->viommu		= viommu;
 
-	return ret > 0 ? 0 : ret;
+	return 0;
 }
 
 static void viommu_domain_free(struct iommu_domain *domain)
-- 
2.20.1