[PATCH AUTOSEL 4.19 442/671] iommu/amd: Make iommu_disable safer

Sasha Levin
2020-01-16T18:49:34Z

From: Kevin Mitchell <kevmitch@arista.com>

[ 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@arista.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 1e9a5da562f0..465f28a7844c 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -422,6 +422,9 @@ 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