CVE-2022-49016

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

net: mdiobus: fix unbalanced node reference count

I got the following report while doing device(mscc-miim) load test with CONFIG_OF_UNITTEST and CONFIG_OF_DYNAMIC enabled:

OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /spi/soc@0/mdio@7107009c/ethernet-phy@0

If the fwnode is not an acpi node, the refcount is get in fwnode_mdiobus_phy_device_register(), but it has never been put when the device is freed in the normal path. So call fwnode_handle_put() in phy_device_release() to avoid leak.

If its an acpi node, it has never been get, but its put in the error path, so call fwnode_handle_get() before phy_device_register() to keep get/put operation balanced.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/2708b357440427d6a9fee667eb7b8307f4625adc
• https://git.kernel.org/stable/c/543d917f691ab06885ee779c862065899eaa4251
• https://git.kernel.org/stable/c/cdde1560118f82498fc9e9a7c1ef7f0ef7755891