iommu: fix KASAN use-after-free in iommu_insert_resv_region

In case the new region gets merged into another one, the nr list node is
freed.  Checking its type while completing the merge algorithm leads to
a use-after-free.  Use new->type instead.

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>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: Stable <stable@vger.kernel.org> #v5.3+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index db7bfd4..1c3f2a3 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -312,8 +312,8 @@ int iommu_insert_resv_region(struct iommu_resv_region *new,
        list_for_each_entry_safe(iter, tmp, regions, list) {
                phys_addr_t top_end, iter_end = iter->start + iter->length - 1;
 
-               /* no merge needed on elements of different types than @nr */
-               if (iter->type != nr->type) {
+               /* no merge needed on elements of different types than @new */
+               if (iter->type != new->type) {
                        list_move_tail(&iter->list, &stack);
                        continue;
                }