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From:   Eric Auger <eric.auger@redhat.com>
To:     eric.auger.pro@gmail.com, eric.auger@redhat.com, joro@8bytes.org,
        hch@lst.de, cai@lca.pw, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] iommu: fix KASAN use-after-free in iommu_insert_resv_region
Date:   Mon, 25 Nov 2019 11:35:35 +0100
Message-Id: <20191125103535.22782-1-eric.auger@redhat.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Store the new region type in a variable. In case the new region
gets merged into another one, the new node is freed and nr shall
not be used anymore.

Fixes: 4dbd258ff63e ("iommu: Revisit iommu_insert_resv_region()
implementation")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Qian Cai <cai@lca.pw>
CC: Stable <stable@vger.kernel.org> #v5.3+
---
 drivers/iommu/iommu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d658c7c6a2ab..338769f96d17 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -293,6 +293,8 @@ int iommu_insert_resv_region(struct iommu_resv_region *=
new,
 =09=09=09     struct list_head *regions)
 {
 =09struct iommu_resv_region *iter, *tmp, *nr, *top;
+=09enum iommu_resv_type nr_type =3D new->type;
+
 =09LIST_HEAD(stack);
=20
 =09nr =3D iommu_alloc_resv_region(new->start, new->length,
@@ -313,7 +315,7 @@ int iommu_insert_resv_region(struct iommu_resv_region *=
new,
 =09=09phys_addr_t top_end, iter_end =3D iter->start + iter->length - 1;
=20
 =09=09/* no merge needed on elements of different types than @nr */
-=09=09if (iter->type !=3D nr->type) {
+=09=09if (iter->type !=3D nr_type) {
 =09=09=09list_move_tail(&iter->list, &stack);
 =09=09=09continue;
 =09=09}
--=20
2.20.1