CVE-2023-53446

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

PCI/ASPM: Disable ASPM on MFD function removal to avoid use-after-free

Struct pcie_link_state->downstream is a pointer to the pci_dev of function 0. Previously we retained that pointer when removing function 0, and subsequent ASPM policy changes dereferenced it, resulting in a use-after-free warning from KASAN, e.g.:

echo 1 > /sys/bus/pci/devices/0000:03:00.0/remove

echo powersave > /sys/module/pcie_aspm/parameters/policy

BUG: KASAN: slab-use-after-free in pcie_config_aspm_link+0x42d/0x500 Call Trace: kasan_report+0xae/0xe0 pcie_config_aspm_link+0x42d/0x500 pcie_aspm_set_policy+0x8e/0x1a0 param_attr_store+0x162/0x2c0 module_attr_store+0x3e/0x80

PCIe spec r6.0, sec 7.5.3.7, recommends that software program the same ASPM Control value in all functions of multi-function devices.

Disable ASPM and free the pcie_link_state when any child function is removed so we can discard the dangling pcie_link_state->downstream pointer and maintain the same ASPM Control configuration for all functions.

[bhelgaas: commit log and comment]

A use-after-free in the PCIe ASPM code could be triggered when function 0 of a multi-function device is removed and the ASPM policy is changed afterwards, leading to a dangling downstream pointer and kernel crash. The issue is locally triggerable only by a privileged user (e.g., via /sys/bus/pci/devices/.../remove and /sys/module/pcie_aspm/parameters/policy) and requires specific PCIe hardware/ASPM configuration.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.