All of
 help / color / mirror / Atom feed
From: Tong Zhang <>
To: Arnd Bergmann <>,
	Greg Kroah-Hartman <>,
	Tong Zhang <>,
Cc: Colin Ian King <>
Subject: [PATCH v4] misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge
Date: Tue, 18 May 2021 15:28:18 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

There is an issue with the ASPM(optional) capability checking function.
A device might be attached to root complex directly, in this case,
bus->self(bridge) will be NULL, thus priv->parent_pdev is NULL.
Since alcor_pci_init_check_aspm(priv->parent_pdev) checks the PCI link's
ASPM capability and populate parent_cap_off, which will be used later by
alcor_pci_aspm_ctrl() to dynamically turn on/off device, what we can do
here is to avoid checking the capability if we are on the root complex.
This will make pdev_cap_off 0 and alcor_pci_aspm_ctrl() will simply
return when bring called, effectively disable ASPM for the device.

[    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 <>
Co-developed-by: Greg Kroah-Hartman <>
Co-developed-by: Colin Ian King <>
v2: check before calling alcor_pci_find_cap_offset()
v3: Add comment. Enable the dev_dbg() output when priv->parent_pdev is NULL.
v4: fix inverted if statement, thanks to Colin <>

 drivers/misc/cardreader/alcor_pci.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/cardreader/alcor_pci.c b/drivers/misc/cardreader/alcor_pci.c
index cd402c89189e..de6d44a158bb 100644
--- a/drivers/misc/cardreader/alcor_pci.c
+++ b/drivers/misc/cardreader/alcor_pci.c
@@ -139,7 +139,13 @@ 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);
-	priv->parent_cap_off = alcor_pci_find_cap_offset(priv,
+	/*
+	 * A device might be attached to root complex directly and
+	 * priv->parent_pdev will be NULL. In this case we don't check its
+	 * capability and disable ASPM completely.
+	 */
+	if (priv->parent_pdev)
+		priv->parent_cap_off = alcor_pci_find_cap_offset(priv,
 	if ((priv->pdev_cap_off == 0) || (priv->parent_cap_off == 0)) {

  parent reply	other threads:[~2021-05-18 19:28 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-18 18:32 misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge Colin Ian King
2021-05-18 19:22 ` Tong Zhang
2021-05-18 19:28 ` Tong Zhang [this message]
2021-05-21 12:44   ` [PATCH v4] " Greg Kroah-Hartman
2021-05-21 14:51     ` Tong Zhang
2021-05-22  4:37     ` [PATCH v1] misc: alcor_pci: fix inverted branch condition Tong Zhang
2021-05-22  4:40     ` [PATCH v4] misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge Tong Zhang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.