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

Vulnerability Description

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]

References

• https://git.kernel.org/stable/c/666e7f9d60cee23077ea3e6331f6f8a19f7ea03f
• https://git.kernel.org/stable/c/7badf4d6f49a358a01ab072bbff88d3ee886c33b
• https://git.kernel.org/stable/c/9856c0de49052174ab474113f4ba40c02aaee086
• https://git.kernel.org/stable/c/7aecdd47910c51707696e8b0e045b9f88bd4230f
• https://git.kernel.org/stable/c/d51d2eeae4ce54d542909c4d9d07bf371a78592c
• https://git.kernel.org/stable/c/4203722d51afe3d239e03f15cc73efdf023a7103
• https://git.kernel.org/stable/c/456d8aa37d0f56fc9e985e812496e861dcd6f2f2