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misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge

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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]

Co-developed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Link: https://lore.kernel.org/r/20210513040732.1310159-1-ztong0001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tong Zhang 2021-05-13 00:07:33 -04:00 committed by Greg Kroah-Hartman
parent 7272b591c4
commit 3ce3e45cc3
1 changed files with 7 additions and 1 deletions
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8
drivers/misc/cardreader/alcor_pci.c
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@ -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,
priv->parent_pdev);
if ((priv->pdev_cap_off == 0) || (priv->parent_cap_off == 0)) {