CVE-2022-49926

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

net: dsa: Fix possible memory leaks in dsa_loop_init()

kmemleak reported memory leaks in dsa_loop_init():

kmemleak: 12 new suspected memory leaks

unreferenced object 0xffff8880138ce000 (size 2048): comm modprobe, pid 390, jiffies 4295040478 (age 238.976s) backtrace: [<000000006a94f1d5>] kmalloc_trace+0x26/0x60 [<00000000a9c44622>] phy_device_create+0x5d/0x970 [<00000000d0ee2afc>] get_phy_device+0xf3/0x2b0 [<00000000dca0c71f>] __fixed_phy_register.part.0+0x92/0x4e0 [<000000008a834798>] fixed_phy_register+0x84/0xb0 [<0000000055223fcb>] dsa_loop_init+0xa9/0x116 [dsa_loop] …

There are two reasons for memleak in dsa_loop_init().

First, fixed_phy_register() create and register phy_device:

fixed_phy_register() get_phy_device() phy_device_create() # freed by phy_device_free() phy_device_register() # freed by phy_device_remove()

But fixed_phy_unregister() only calls phy_device_remove(). So the memory allocated in phy_device_create() is leaked.

Second, when mdio_driver_register() fail in dsa_loop_init(), it just returns and there is no cleanup for phydevs.

Fix the problems by catching the error of mdio_driver_register() in dsa_loop_init(), then calling both fixed_phy_unregister() and phy_device_free() to release phydevs. Also add a function for phydevs cleanup to avoid duplacate.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

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/37a098fc9b42bd7fce66764866aa514639667b6e
• https://git.kernel.org/stable/c/4d2024b138d9f7b02ae13ee997fd3a71e9e46254
• https://git.kernel.org/stable/c/633efc8b3dc96f56f5a57f2a49764853a2fa3f50
• https://git.kernel.org/stable/c/935b4beb724946a37cebf97191592d4879d3a3a3
• https://git.kernel.org/stable/c/9f555b1584fc2d5d16ee3c4d9438e93ac7c502c7
• https://git.kernel.org/stable/c/bbc5d7b46a729bfcbb5544f6612b7a67dd4f4d6f
• https://git.kernel.org/stable/c/d593e1ede655b74c42e4e4fe285ea64aee96fb5c