CVE-2024-42302 PCI/DPC: Fix use-after-free on concurrent DPC and hot-removal
A use-after-free in the Linux kernel PCI/DPC handler allows a local attacker to cause a system crash via concurrent hot-removal and DPC events.
- 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-2024-42302?
CVE-2024-42302 is a high-severity use after free vulnerability in Debian Debian Linux, published on 17 Aug 2024. 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/DPC: Fix use-after-free on concurrent DPC and hot-removal
Keith reports a use-after-free when a DPC event occurs concurrently to hot-removal of the same portion of the hierarchy:
The dpc_handler() awaits readiness of the secondary bus below the Downstream Port where the DPC event occurred. To do so, it polls the config space of the first child device on the secondary bus. If that child device is concurrently removed, accesses to its struct pci_dev cause the kernel to oops.
That's because pci_bridge_wait_for_secondary_bus() neglects to hold a reference on the child device. Before v6.3, the function was only called on resume from system sleep or on runtime resume. Holding a reference wasn't necessary back then because the pciehp IRQ thread could never run concurrently. (On resume from system sleep, IRQs are not enabled until after the resume_noirq phase. And runtime resume is always awaited before a PCI device is removed.)
However starting with v6.3, pci_bridge_wait_for_secondary_bus() is also called on a DPC event. Commit 53b54ad074de ("PCI/DPC: Await readiness of secondary bus after reset"), which introduced that, failed to appreciate that pci_bridge_wait_for_secondary_bus() now needs to hold a reference on the child device because dpc_handler() and pciehp may indeed run concurrently. The commit was backported to v5.10+ stable kernels, so that's the oldest one affected.
Add the missing reference acquisition.
Abridged stack trace:
BUG: unable to handle page fault for address: 00000000091400c0 CPU: 15 PID: 2464 Comm: irq/53-pcie-dpc 6.9.0 RIP: pci_bus_read_config_dword+0x17/0x50 pci_dev_wait() pci_bridge_wait_for_secondary_bus() dpc_reset_link() pcie_do_recovery() dpc_handler()
Weakness: CWE-416
Which versions are affected by CVE-2024-42302?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2024-42302?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2024-42302 being exploited?
There is no known exploitation of CVE-2024-42302 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-47962, AZL-48048, BELL-CVE-2024-42302, DEBIAN-CVE-2024-42302, GHSA-37c4-pj3v-mf79, UBUNTU-CVE-2024-42302.