[PATCH 4.19 169/321] vfio/spapr_tce: Get rid of possible infinite loop

Greg Kroah-Hartman
2019-12-03T23:02:29Z

From: Alexey Kardashevskiy <aik@ozlabs.ru>

[ Upstream commit 517ad4ae8aa93dccdb9a88c27257ecb421c9e848 ]

As a part of cleanup, the SPAPR TCE IOMMU subdriver releases preregistered
memory. If there is a bug in memory release, the loop in
tce_iommu_release() becomes infinite; this actually happened to me.

This makes the loop finite and prints a warning on every failure to make
the code more bug prone.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/vfio/vfio_iommu_spapr_tce.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 96721b154454f..ec53310f16136 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -371,6 +371,7 @@ static void tce_iommu_release(void *iommu_data)
{
struct tce_container *container = iommu_data;
struct tce_iommu_group *tcegrp;
+ struct tce_iommu_prereg *tcemem, *tmtmp;
long i;

while (tce_groups_attached(container)) {
@@ -393,13 +394,8 @@ static void tce_iommu_release(void *iommu_data)
tce_iommu_free_table(container, tbl);
}

- while (!list_empty(&container->prereg_list)) {
- struct tce_iommu_prereg *tcemem;
-
- tcemem = list_first_entry(&container->prereg_list,
- struct tce_iommu_prereg, next);
- WARN_ON_ONCE(tce_iommu_prereg_free(container, tcemem));
- }
+ list_for_each_entry_safe(tcemem, tmtmp, &container->prereg_list, next)
+ WARN_ON(tce_iommu_prereg_free(container, tcemem));

tce_iommu_disable(container);
if (container->mm)
--
2.20.1