iommu/amd: Fix potential @entry null deref

[ Upstream commit 14c4acc5ed22c21f9821103be7c48efdf9763584 ]

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.

Fixes: 26e495f34107 ("iommu/amd: Restore IRTE.RemapEn bit after programming IRTE")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20200910171621.12879-1-joao.m.martins@oracle.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 37c74c842f3a37f92cda6f2c8d41798fccb257a0..48fe272da6e9c4e1ba583396d73c155c5ea7d66c 100644 (file)
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3855,12 +3855,14 @@ 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;