linux-kernel - [PATCH AUTOSEL 4.14 03/28] iommu/vt-d: Fix mm reference leak

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Date:   Sat, 18 Apr 2020 10:43:03 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>,
        Sasha Levin <sashal@...nel.org>,
        iommu@...ts.linux-foundation.org
Subject: [PATCH AUTOSEL 4.14 03/28] iommu/vt-d: Fix mm reference leak

From: Jacob Pan <jacob.jun.pan@...ux.intel.com>

[ Upstream commit 902baf61adf6b187f0a6b789e70d788ea71ff5bc ]

Move canonical address check before mmget_not_zero() to avoid mm
reference leak.

Fixes: 9d8c3af31607 ("iommu/vt-d: IOMMU Page Request needs to check if address is canonical.")
Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/iommu/intel-svm.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index f5573bb9f450e..837459762eb39 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -613,14 +613,15 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 		 * any faults on kernel addresses. */
 		if (!svm->mm)
 			goto bad_req;
-		/* If the mm is already defunct, don't handle faults. */
-		if (!mmget_not_zero(svm->mm))
-			goto bad_req;
 
 		/* If address is not canonical, return invalid response */
 		if (!is_canonical_address(address))
 			goto bad_req;
 
+		/* If the mm is already defunct, don't handle faults. */
+		if (!mmget_not_zero(svm->mm))
+			goto bad_req;
+
 		down_read(&svm->mm->mmap_sem);
 		vma = find_extend_vma(svm->mm, address);
 		if (!vma || address < vma->vm_start)
-- 
2.20.1