CVE-2022-49842

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

ASoC: core: Fix use-after-free in snd_soc_exit()

KASAN reports a use-after-free:

BUG: KASAN: use-after-free in device_del+0xb5b/0xc60 Read of size 8 at addr ffff888008655050 by task rmmod/387 CPU: 2 PID: 387 Comm: rmmod Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Call Trace: dump_stack_lvl+0x79/0x9a print_report+0x17f/0x47b kasan_report+0xbb/0xf0 device_del+0xb5b/0xc60 platform_device_del.part.0+0x24/0x200 platform_device_unregister+0x2e/0x40 snd_soc_exit+0xa/0x22 [snd_soc_core] __do_sys_delete_module.constprop.0+0x34f/0x5b0 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd …

Its bacause in snd_soc_init(), snd_soc_util_init() is possble to fail, but its ret is ignored, which makes soc_dummy_dev unregistered twice.

snd_soc_init() snd_soc_util_init() platform_device_register_simple(soc_dummy_dev) platform_driver_register() # fail platform_device_unregister(soc_dummy_dev) platform_driver_register() # success … snd_soc_exit() snd_soc_util_exit() # soc_dummy_dev will be unregistered for second time

To fix it, handle error and stop snd_soc_init() when util_init() fail. Also clean debugfs when util_init() or driver_register() fail.

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/2ec3f558db343b045a7c7419cdbaec266b8ac1a7
• https://git.kernel.org/stable/c/34eee4189bcebbd5f6a2ff25ef0cb893ad33d51e
• https://git.kernel.org/stable/c/41fad4f712e081acdfde8b59847f9f66eaf407a0
• https://git.kernel.org/stable/c/6ec27c53886c8963729885bcf2dd996eba2767a7
• https://git.kernel.org/stable/c/8d21554ec7680e9585fb852d933203c3db60dad1
• https://git.kernel.org/stable/c/90bbdf30a51e42378cb23a312005a022794b8e1e
• https://git.kernel.org/stable/c/a3365e62239dc064019a244bde5686ac18527c22
• https://git.kernel.org/stable/c/c5674bd073c0fd9f620ca550c5ff08d0d429bdd9