The riscv_iommu_pte_fetch can return NULL when the provided iova is not
yet mapped, the caller should check if the returned pointer is NULL or
not, but riscv_iommu_iova_to_phys missed this, which will then lead to
a kernel panic.

Check the pointer before using it to avoid the bug. Now, when
iova_to_phys is called with an unmapped iova, the kernel will not crash
here.

Changelog
---------
v2:
- Update change description
- Add "Fixes" tag

Fixes: 488ffbf18171 ("iommu/riscv: Paging domain support")
Cc: Tomasz Jeznach <tjeznach@rivosinc.com>
Signed-off-by: XianLiang Huang <huangxianliang@lanxincomputing.com>
---
 drivers/iommu/riscv/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index 2d0d31ba2886..b0186faa0300 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -1283,7 +1283,7 @@ static phys_addr_t riscv_iommu_iova_to_phys(struct iommu_domain *iommu_domain,
 	unsigned long *ptr;
 
 	ptr = riscv_iommu_pte_fetch(domain, iova, &pte_size);
-	if (_io_pte_none(*ptr) || !_io_pte_present(*ptr))
+	if (!ptr || _io_pte_none(*ptr) || !_io_pte_present(*ptr))
 		return 0;
 
 	return pfn_to_phys(__page_val_to_pfn(*ptr)) | (iova & (pte_size - 1));
-- 
2.34.1