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, run insert_iommu_master(dev, &iommu, spec); unlock and
return 0 when found, otherwise unlock and return -ENODEV.

Cc: sta...@vger.kernel.org
Fixes: f78ebca8ff3d6 ("iommu/msm: Add support for generic master bindings")
Signed-off-by: Xiaomeng Tong <xiam0nd.t...@gmail.com>
---
 drivers/iommu/msm_iommu.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 3a38352b603f..1dbb8b0695ec 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -617,23 +617,17 @@ static int qcom_iommu_of_xlate(struct device *dev,
 {
        struct msm_iommu_dev *iommu;
        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)
-                       break;
-
-       if (!iommu || iommu->dev->of_node != spec->np) {
-               ret = -ENODEV;
-               goto fail;
-       }
-
-       insert_iommu_master(dev, &iommu, spec);
-fail:
+               if (iommu->dev->of_node == spec->np) {
+                       insert_iommu_master(dev, &iommu, spec);
+                       spin_unlock_irqrestore(&msm_iommu_lock, flags);
+                       return 0;
+               }
        spin_unlock_irqrestore(&msm_iommu_lock, flags);
 
-       return ret;
+       return -ENODEV;
 }
 
 irqreturn_t msm_iommu_fault_handler(int irq, void *dev_id)
-- 
2.17.1

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