[PATCH 5.10 053/120] thunderbolt: Fix possible NULL pointer dereference in tb_acpi_add_link()

[Greg Kroah-Hartman]

From: Mario Limonciello <mario.limonciello@xxxxxxxx>

commit 4d395c5e74398f664405819330e5a298da37f655 upstream.

When we walk up the device hierarchy in tb_acpi_add_link() make sure we
break the loop if the device has no parent. Otherwise we may crash the
kernel by dereferencing a NULL pointer.

Fixes: b2be2b05cf3b ("thunderbolt: Create device links from ACPI description")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
Acked-by: Yehezkel Bernat <YehezkelShB@xxxxxxxxx>
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/thunderbolt/acpi.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/thunderbolt/acpi.c
+++ b/drivers/thunderbolt/acpi.c
@@ -56,7 +56,7 @@ static acpi_status tb_acpi_add_link(acpi
 	 * managed with the xHCI and the SuperSpeed hub so we create the
 	 * link from xHCI instead.
 	 */
-	while (!dev_is_pci(dev))
+	while (dev && !dev_is_pci(dev))
 		dev = dev->parent;
 
 	if (!dev)