[PATCH 4.4 107/183] iommu/amd: Make iommu_disable safer

[Greg Kroah-Hartman]

From: Kevin Mitchell <kevmitch@xxxxxxxxxx>

[ Upstream commit 3ddbe913e55516d3e2165d43d4d5570761769878 ]

Make it safe to call iommu_disable during early init error conditions
before mmio_base is set, but after the struct amd_iommu has been added
to the amd_iommu_list. For example, this happens if firmware fails to
fill in mmio_phys in the ACPI table leading to a NULL pointer
dereference in iommu_feature_disable.

Fixes: 2c0ae1720c09c ('iommu/amd: Convert iommu initialization to state machine')
Signed-off-by: Kevin Mitchell <kevmitch@xxxxxxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/iommu/amd_iommu_init.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 6a69b5bb231f8..036fb186a3bef 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -360,6 +360,9 @@ static void iommu_enable(struct amd_iommu *iommu)
 
 static void iommu_disable(struct amd_iommu *iommu)
 {
+	if (!iommu->mmio_base)
+		return;
+
 	/* Disable command buffer */
 	iommu_feature_disable(iommu, CONTROL_CMDBUF_EN);
 
-- 
2.20.1