[PATCH 5.8 073/118] iommu/amd: Fix potential @entry null deref

Greg Kroah-Hartman
2020-09-21T16:55:46Z

From: Joao Martins <joao.m.martins@oracle.com>

[ 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>
---
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 37c74c842f3a3..48fe272da6e9c 100644
--- 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;

--
2.25.1