[PATCH v2] misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge

[Tong Zhang]

Device might be attached to root complex directly. In this case,
bus->self(bridge) will be NULL, so we'd better check before use it

[    1.246492] BUG: kernel NULL pointer dereference, address: 00000000000000c0
[    1.248731] RIP: 0010:pci_read_config_byte+0x5/0x40
[    1.253998] Call Trace:
[    1.254131]  ? alcor_pci_find_cap_offset.isra.0+0x3a/0x100 [alcor_pci]
[    1.254476]  alcor_pci_probe+0x169/0x2d5 [alcor_pci]

Signed-off-by: Tong Zhang <ztong0001@xxxxxxxxx>
Co-Developed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
v2: check before calling alcor_pci_find_cap_offset()

 drivers/misc/cardreader/alcor_pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/misc/cardreader/alcor_pci.c b/drivers/misc/cardreader/alcor_pci.c
index cd402c89189e..175c6b06f7aa 100644
--- a/drivers/misc/cardreader/alcor_pci.c
+++ b/drivers/misc/cardreader/alcor_pci.c
@@ -139,6 +139,9 @@ static void alcor_pci_init_check_aspm(struct alcor_pci_priv *priv)
 	u32 val32;
 
 	priv->pdev_cap_off    = alcor_pci_find_cap_offset(priv, priv->pdev);
+
+	if (!priv->parent_pdev)
+		return;
 	priv->parent_cap_off = alcor_pci_find_cap_offset(priv,
 							 priv->parent_pdev);
 
-- 
2.25.1