diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c
index 4e66473d7cea..4c53b6361314 100644
--- a/drivers/iommu/amd/debugfs.c
+++ b/drivers/iommu/amd/debugfs.c
@@ -31,11 +31,12 @@ static ssize_t iommu_mmio_write(struct file *filp, const char __user *ubuf,
 	if (cnt > OFS_IN_SZ)
 		return -EINVAL;
 
-	ret = kstrtou32_from_user(ubuf, cnt, 0, &dbg_mmio_offset);
+	ret = kstrtos32_from_user(ubuf, cnt, 0, &dbg_mmio_offset);
 	if (ret)
 		return ret;
 
-	if (dbg_mmio_offset > iommu->mmio_phys_end - sizeof(u64))
+	if (dbg_mmio_offset < 0 || dbg_mmio_offset >
+			iommu->mmio_phys_end - sizeof(u64))
 		return -EINVAL;
 
 	iommu->dbg_mmio_offset = dbg_mmio_offset;
@@ -71,12 +72,12 @@ static ssize_t iommu_capability_write(struct file *filp, const char __user *ubuf
 	if (cnt > OFS_IN_SZ)
 		return -EINVAL;
 
-	ret = kstrtou32_from_user(ubuf, cnt, 0, &dbg_cap_offset);
+	ret = kstrtos32_from_user(ubuf, cnt, 0, &dbg_cap_offset);
 	if (ret)
 		return ret;
 
 	/* Capability register at offset 0x14 is the last IOMMU capability register. */
-	if (dbg_cap_offset > 0x14)
+	if (dbg_cap_offset < 0 || dbg_cap_offset > 0x14)
 		return -EINVAL;
 
 	iommu->dbg_cap_offset = dbg_cap_offset;