CVE-2021-47283

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

net:sfc: fix non-freed irq in legacy irq mode

SFC driver can be configured via modparam to work using MSI-X, MSI or legacy IRQ interrupts. In the last one, the interrupt was not properly released on module remove.

It was not freed because the flag irqs_hooked was not set during initialization in the case of using legacy IRQ.

Example of (trimmed) trace during module remove without this fix:

remove_proc_entry: removing non-empty directory irq/125, leaking at least 0000:3b:00.1 WARNING: CPU: 39 PID: 3658 at fs/proc/generic.c:715 remove_proc_entry+0x15c/0x170 …trimmed… Call Trace: unregister_irq_proc+0xe3/0x100 free_desc+0x29/0x70 irq_free_descs+0x47/0x70 mp_unmap_irq+0x58/0x60 acpi_unregister_gsi_ioapic+0x2a/0x40 acpi_pci_irq_disable+0x78/0xb0 pci_disable_device+0xd1/0x100 efx_pci_remove+0xa1/0x1e0 [sfc] pci_device_remove+0x38/0xa0 __device_release_driver+0x177/0x230 driver_detach+0xcb/0x110 bus_remove_driver+0x58/0xd0 pci_unregister_driver+0x2a/0xb0 efx_exit_module+0x24/0xf40 [sfc] __do_sys_delete_module.constprop.0+0x171/0x280 ? exit_to_user_mode_prepare+0x83/0x1d0 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f9f9385800b …trimmed…

Weakness

The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, languages such as Java, Ruby, and Lisp perform automatic garbage collection that releases memory for objects that have been deallocated.
• Use resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems.
• When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged users; alternately, begin releasing resources for less-privileged users. While this mitigation may protect the system from attack, it will not necessarily stop attackers from adversely impacting other users.
• Ensure that the application performs the appropriate error checks and error handling in case resources become unavailable (CWE-703).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/469.html

References

• https://git.kernel.org/stable/c/81c4d1d83f88e15b26f4522a35cba6ffd8c5dfdd
• https://git.kernel.org/stable/c/8d717c9135a3340ae62d1699484850bfb4112b0c
• https://git.kernel.org/stable/c/8f03eeb6e0a0a0b8d617ee0a4bce729e47130036
• https://git.kernel.org/stable/c/81c4d1d83f88e15b26f4522a35cba6ffd8c5dfdd
• https://git.kernel.org/stable/c/8d717c9135a3340ae62d1699484850bfb4112b0c
• https://git.kernel.org/stable/c/8f03eeb6e0a0a0b8d617ee0a4bce729e47130036