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

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Message-Id: <20210511212937.1269191-1-ztong0001@gmail.com>
Date:   Tue, 11 May 2021 17:29:38 -0400
From:   Tong Zhang <ztong0001@...il.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tong Zhang <ztong0001@...il.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2] misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge

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@...il.com>
Co-Developed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
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