[PATCH] iommu/amd: Fix potential @entry null deref

[Joao Martins]

After commit 26e495f34107 ("iommu/amd: Restore IRTE.RemapEn bit after
programming IRTE"), smatch warns:

        drivers/iommu/amd/iommu.c:3870 amd_iommu_deactivate_guest_mode()
        warn: variable dereferenced before check 'entry' (see line 3867)

Fix this by moving the @valid assignment to after @entry has been checked
for NULL.

Cc: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com>
Fixes: 26e495f34107 ("iommu/amd: Restore IRTE.RemapEn bit after programming 
IRTE")
Reported-by: Dan Carpenter <dan.carpen...@oracle.com>
Signed-off-by: Joao Martins <joao.m.mart...@oracle.com>
---
 drivers/iommu/amd/iommu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 07ae8b93887e..8abe1c7ad45b 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3864,12 +3864,14 @@ int amd_iommu_deactivate_guest_mode(void *data)
        struct amd_ir_data *ir_data = (struct amd_ir_data *)data;
        struct irte_ga *entry = (struct irte_ga *) ir_data->entry;
        struct irq_cfg *cfg = ir_data->cfg;
-       u64 valid = entry->lo.fields_remap.valid;
+       u64 valid;
 
        if (!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir) ||
            !entry || !entry->lo.fields_vapic.guest_mode)
                return 0;
 
+       valid = entry->lo.fields_remap.valid;
+
        entry->lo.val = 0;
        entry->hi.val = 0;
 
-- 
2.17.1