CVE-2024-46798

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

ASoC: dapm: Fix UAF for snd_soc_pcm_runtime object

When using kernel with the following extra config,

• CONFIG_KASAN=y
• CONFIG_KASAN_GENERIC=y
• CONFIG_KASAN_INLINE=y
• CONFIG_KASAN_VMALLOC=y
• CONFIG_FRAME_WARN=4096

kernel detects that snd_pcm_suspend_all() access a freed snd_soc_pcm_runtime object when the system is suspended, which leads to a use-after-free bug:

[ 52.047746] BUG: KASAN: use-after-free in snd_pcm_suspend_all+0x1a8/0x270 [ 52.047765] Read of size 1 at addr ffff0000b9434d50 by task systemd-sleep/2330

[ 52.047785] Call trace: [ 52.047787] dump_backtrace+0x0/0x3c0 [ 52.047794] show_stack+0x34/0x50 [ 52.047797] dump_stack_lvl+0x68/0x8c [ 52.047802] print_address_description.constprop.0+0x74/0x2c0 [ 52.047809] kasan_report+0x210/0x230 [ 52.047815] __asan_report_load1_noabort+0x3c/0x50 [ 52.047820] snd_pcm_suspend_all+0x1a8/0x270 [ 52.047824] snd_soc_suspend+0x19c/0x4e0

The snd_pcm_sync_stop() has a NULL check on substream->runtime before making any access. So we need to always set substream->runtime to NULL everytime we kfree() it.

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/3033ed903b4f28b5e1ab66042084fbc2c48f8624
• https://git.kernel.org/stable/c/5d13afd021eb43868fe03cef6da34ad08831ad6d
• https://git.kernel.org/stable/c/6a14fad8be178df6c4589667efec1789a3307b4e
• https://git.kernel.org/stable/c/8ca21e7a27c66b95a4b215edc8e45e5d66679f9f
• https://git.kernel.org/stable/c/993b60c7f93fa1d8ff296b58f646a867e945ae89
• https://git.kernel.org/stable/c/b4a90b543d9f62d3ac34ec1ab97fc5334b048565
• https://git.kernel.org/stable/c/fe5046ca91d631ec432eee3bdb1f1c49b09c8b5e