[PATCH 5.18 825/879] iommu/msm: Fix an incorrect NULL check on list iterator

Greg Kroah-Hartman
2022-06-08T03:18:39Z

From: Xiaomeng Tong <xiam0nd.tong@gmail.com>

commit 8b9ad480bd1dd25f4ff4854af5685fa334a2f57a upstream.

The bug is here:
if (!iommu || iommu->dev->of_node != spec->np) {

The list iterator value 'iommu' will *always* be set and non-NULL by
list_for_each_entry(), so it is incorrect to assume that the iterator
value will be NULL if the list is empty or no element is found (in fact,
it will point to a invalid structure object containing HEAD).

To fix the bug, use a new value 'iter' as the list iterator, while use
the old value 'iommu' as a dedicated variable to point to the found one,
and remove the unneeded check for 'iommu->dev->of_node != spec->np'
outside the loop.

Cc: stable@vger.kernel.org
Fixes: f78ebca8ff3d6 ("iommu/msm: Add support for generic master bindings")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Link: https://lore.kernel.org/r/20220501132823.12714-1-xiam0nd.tong@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iommu/msm_iommu.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -610,16 +610,19 @@ static void insert_iommu_master(struct d
static int qcom_iommu_of_xlate(struct device *dev,
struct of_phandle_args *spec)
{
- struct msm_iommu_dev *iommu;
+ struct msm_iommu_dev *iommu = NULL, *iter;
unsigned long flags;
int ret = 0;

spin_lock_irqsave(&msm_iommu_lock, flags);
- list_for_each_entry(iommu, &qcom_iommu_devices, dev_node)
- if (iommu->dev->of_node == spec->np)
+ list_for_each_entry(iter, &qcom_iommu_devices, dev_node) {
+ if (iter->dev->of_node == spec->np) {
+ iommu = iter;
break;
+ }
+ }

- if (!iommu || iommu->dev->of_node != spec->np) {
+ if (!iommu) {
ret = -ENODEV;
goto fail;
}