[PATCH 5.6 015/126] iommu/amd: Fix get_acpihid_device_id()

[Greg Kroah-Hartman]

From: Raul E Rangel <rrangel@xxxxxxxxxxxx>

[ Upstream commit ea90228c7b2ae6646bb6381385229aabb6f14cd2 ]

acpi_dev_hid_uid_match() expects a null pointer for UID if it doesn't
exist. The acpihid_map_entry contains a char buffer for holding the
UID. If no UID was provided in the IVRS table, this buffer will be
zeroed. If we pass in a null string, acpi_dev_hid_uid_match() will
return false because it will try and match an empty string to the ACPI
UID of the device.

Fixes: ae5e6c6439c3 ("iommu/amd: Switch to use acpi_dev_hid_uid_match()")
Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Raul E Rangel <rrangel@xxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Link: https://lore.kernel.org/r/20200511103229.v2.1.I6f1b6f973ee6c8af1348611370c73a0ec0ea53f1@changeid
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/iommu/amd_iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 500d0a8c966f..1d8634250afc 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -127,7 +127,8 @@ static inline int get_acpihid_device_id(struct device *dev,
 		return -ENODEV;
 
 	list_for_each_entry(p, &acpihid_map, list) {
-		if (acpi_dev_hid_uid_match(adev, p->hid, p->uid)) {
+		if (acpi_dev_hid_uid_match(adev, p->hid,
+					   p->uid[0] ? p->uid : NULL)) {
 			if (entry)
 				*entry = p;
 			return p->devid;
-- 
2.25.1