CVE-2021-46930

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

usb: mtu3: fix list_head check warning

This is caused by uninitialization of list_head.

BUG: KASAN: use-after-free in __list_del_entry_valid+0x34/0xe4

Call trace: dump_backtrace+0x0/0x298 show_stack+0x24/0x34 dump_stack+0x130/0x1a8 print_address_description+0x88/0x56c __kasan_report+0x1b8/0x2a0 kasan_report+0x14/0x20 __asan_load8+0x9c/0xa0 __list_del_entry_valid+0x34/0xe4 mtu3_req_complete+0x4c/0x300 [mtu3] mtu3_gadget_stop+0x168/0x448 [mtu3] usb_gadget_unregister_driver+0x204/0x3a0 unregister_gadget_item+0x44/0xa4

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/249ddfbe00570d6dc76208e88017937d4d374c79
• https://git.kernel.org/stable/c/3b6efe0b7ba03cc2acf0694b46d6ff33c5b4c295
• https://git.kernel.org/stable/c/585e2b244dda7ea733274e4b8fa27853d625d3bf
• https://git.kernel.org/stable/c/8c313e3bfd9adae8d5c4ba1cc696dcbc86fbf9bf