CVE-2026-53051

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

PCI: tegra194: Fix CBB timeout caused by DBI access before core power-on

When PERST# is deasserted twice (assert -> deassert -> assert -> deassert),

a CBB (Control Backbone) timeout occurs at DBI register offset 0x8bc

(PCIE_MISC_CONTROL_1_OFF). This happens because pci_epc_deinit_notify()

and dw_pcie_ep_cleanup() are called before reset_control_deassert() powers

on the controller core.

The call chain that causes the timeout:

pex_ep_event_pex_rst_deassert()

pci_epc_deinit_notify()

pci_epf_test_epc_deinit()

pci_epf_test_clear_bar()

pci_epc_clear_bar()

dw_pcie_ep_clear_bar()

__dw_pcie_ep_reset_bar()

dw_pcie_dbi_ro_wr_en() <- Accesses 0x8bc DBI register

reset_control_deassert(pcie->core_rst) <- Core powered on HERE

The DBI registers, including PCIE_MISC_CONTROL_1_OFF (0x8bc), are only

accessible after the controller core is powered on via

reset_control_deassert(pcie->core_rst). Accessing them before this point

results in a CBB timeout because the hardware is not yet operational.

Fix this by moving pci_epc_deinit_notify() and dw_pcie_ep_cleanup() to

after reset_control_deassert(pcie->core_rst), ensuring the controller is

fully powered on before any DBI register accesses occur.