CVE-2025-22031 PCI/bwctrl: Fix NULL pointer dereference on bus number exhaustion
A NULL pointer dereference in the Linux kernel PCI bandwidth controller can cause a system crash when bus numbers are exhausted.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-22031?
CVE-2025-22031 is a medium-severity vulnerability in Linux kernel, published on 16 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
PCI/bwctrl: Fix NULL pointer dereference on bus number exhaustion
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
Weakness: CWE-476
Which versions are affected by CVE-2025-22031?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-22031?
Apply the vendor's patch.
Is CVE-2025-22031 being exploited?
There is no known exploitation of CVE-2025-22031 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-22031, GHSA-2788-7prj-r2qv, ROOT-OS-DEBIAN-13-CVE-2025-22031, UBUNTU-CVE-2025-22031.