iommu/amd: Fix incorrect error handling in amd_iommu_bind_pasid()

In function amd_iommu_bind_pasid(), the control flow jumps
to label out_free when pasid_state->mm and mm is NULL. And
mmput(mm) is called.  In function mmput(mm), mm is
referenced without validation. This will result in a NULL
dereference bug. This patch fixes the bug.

Signed-off-by: Pan Bian <bianpan2016@163.com>
Fixes: f0aac63b873b ('iommu/amd: Don't hold a reference to mm_struct')
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 063343909b0d12f31fac8682058b2eaed4ad2b91..6629c472eafd828bb45a9e7fe3a4260c2e199de2 100644 (file)
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -696,9 +696,9 @@ out_clear_state:
 
 out_unregister:
        mmu_notifier_unregister(&pasid_state->mn, mm);
+       mmput(mm);
 
 out_free:
-       mmput(mm);
        free_pasid_state(pasid_state);
 
 out: