CVE-2022-50269

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

drm/vkms: Fix memory leak in vkms_init()

A memory leak was reported after the vkms module install failed.

unreferenced object 0xffff88810bc28520 (size 16): comm modprobe, pid 9662, jiffies 4298009455 (age 42.590s) hex dump (first 16 bytes): 01 01 00 64 81 88 ff ff 00 00 dc 0a 81 88 ff ff …d………… backtrace: [<00000000e7561ff8>] kmalloc_trace+0x27/0x60 [<000000000b1954a0>] 0xffffffffc45200a9 [<00000000abbf1da0>] do_one_initcall+0xd0/0x4f0 [<000000001505ee87>] do_init_module+0x1a4/0x680 [<00000000958079ad>] load_module+0x6249/0x7110 [<00000000117e4696>] __do_sys_finit_module+0x140/0x200 [<00000000f74b12d2>] do_syscall_64+0x35/0x80 [<000000008fc6fcde>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

The reason is that the vkms_init() returns without checking the return value of vkms_create(), and if the vkms_create() failed, the config allocated at the beginning of vkms_init() is leaked.

vkms_init() config = kmalloc(…) # config allocated … return vkms_create() # vkms_create failed and config is leaked

Fix this problem by checking return value of vkms_create() and free the config if error happened.

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/07ab77154d6fd2d67e465ab5ce30083709950f02
• https://git.kernel.org/stable/c/0d0b368b9d104b437e1f4850ae94bdb9a3601e89
• https://git.kernel.org/stable/c/bad13de764888b765ceaa4668893b52bd16653cc
• https://git.kernel.org/stable/c/bebd60ec3bf21062f103e32e6203c6daabdbd51b