linux-kernel - [PATCH 5.4 48/72] iommu/amd: Fix potential @entry null deref

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Date:   Mon, 21 Sep 2020 18:31:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Joerg Roedel <jroedel@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 48/72] iommu/amd: Fix potential @entry null deref

From: Joao Martins <joao.m.martins@...cle.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@...cle.com>
Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Link: https://lore.kernel.org/r/20200910171621.12879-1-joao.m.martins@oracle.com
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.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 cdafc652d9d1a..fa91d856a43ee 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -4431,12 +4431,14 @@ 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