6.14-stable review patch. If anyone has any objections, please let me know.
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From: Lukas Wunner lukas@wunner.de
commit 667f053b05f00a007738cd7ed6fa1901de19dc7e upstream.
When BIOS neglects to assign bus numbers to PCI bridges, the kernel attempts to correct that during PCI device enumeration. If it runs out of bus numbers, no pci_bus is allocated and the "subordinate" pointer in the bridge's pci_dev remains NULL.
The PCIe bandwidth controller erroneously does not check for a NULL subordinate pointer and dereferences it on probe.
Bandwidth control of unusable devices below the bridge is of questionable utility, so simply error out instead. This mirrors what PCIe hotplug does since commit 62e4492c3063 ("PCI: Prevent NULL dereference during pciehp probe").
The PCI core emits a message with KERN_INFO severity if it has run out of bus numbers. PCIe hotplug emits an additional message with KERN_ERR severity to inform the user that hotplug functionality is disabled at the bridge. A similar message for bandwidth control does not seem merited, given that its only purpose so far is to expose an up-to-date link speed in sysfs and throttle the link speed on certain laptops with limited Thermal Design Power. So error out silently.
User-visible messages:
pci 0000:16:02.0: bridge configuration invalid ([bus 00-00]), reconfiguring [...] pci_bus 0000:45: busn_res: [bus 45-74] end is updated to 74 pci 0000:16:02.0: devices behind bridge are unusable because [bus 45-74] cannot be assigned for them [...] pcieport 0000:16:02.0: pciehp: Hotplug bridge without secondary bus, ignoring [...] BUG: kernel NULL pointer dereference RIP: pcie_update_link_speed pcie_bwnotif_enable pcie_bwnotif_probe pcie_port_probe_service really_probe
Fixes: 665745f27487 ("PCI/bwctrl: Re-add BW notification portdrv as PCIe BW controller") Reported-by: Wouter Bijlsma wouter@wouterbijlsma.nl Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219906 Signed-off-by: Lukas Wunner lukas@wunner.de Signed-off-by: Krzysztof Wilczyński kwilczynski@kernel.org Tested-by: Wouter Bijlsma wouter@wouterbijlsma.nl Cc: stable@vger.kernel.org # v6.13+ Link: https://lore.kernel.org/r/3b6c8d973aedc48860640a9d75d20528336f1f3c.174266937... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/pcie/bwctrl.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/pci/pcie/bwctrl.c +++ b/drivers/pci/pcie/bwctrl.c @@ -294,6 +294,10 @@ static int pcie_bwnotif_probe(struct pci struct pci_dev *port = srv->port; int ret;
+ /* Can happen if we run out of bus numbers during enumeration. */ + if (!port->subordinate) + return -ENODEV; + struct pcie_bwctrl_data *data = devm_kzalloc(&srv->device, sizeof(*data), GFP_KERNEL); if (!data)