CVE-2021-47333

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

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

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]

[

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References