CVE-2024-35955

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

kprobes: Fix possible use-after-free issue on kprobe registration

When unloading a module, its state is changing MODULE_STATE_LIVE -> MODULE_STATE_GOING -> MODULE_STATE_UNFORMED. Each change will take a time. is_module_text_address() and __module_text_address() works with MODULE_STATE_LIVE and MODULE_STATE_GOING. If we use is_module_text_address() and __module_text_address() separately, there is a chance that the first one is succeeded but the next one is failed because module->state becomes MODULE_STATE_UNFORMED between those operations.

In check_kprobe_address_safe(), if the second __module_text_address() is failed, that is ignored because it expected a kernel_text address. But it may have failed simply because module->state has been changed to MODULE_STATE_UNFORMED. In this case, arm_kprobe() will try to modify non-exist module text address (use-after-free).

To fix this problem, we should not use separated is_module_text_address() and __module_text_address(), but use only __module_text_address() once and do try_module_get(module) which is only available with MODULE_STATE_LIVE.

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/2df2dd27066cdba8041e46a64362325626bdfb2e
• https://git.kernel.org/stable/c/325f3fb551f8cd672dbbfc4cf58b14f9ee3fc9e8
• https://git.kernel.org/stable/c/36b57c7d2f8b7de224980f1a284432846ad71ca0
• https://git.kernel.org/stable/c/5062d1f4f07facbdade0f402d9a04a788f52e26d
• https://git.kernel.org/stable/c/62029bc9ff2c17a4e3a2478d83418ec575413808
• https://git.kernel.org/stable/c/93eb31e7c3399e326259f2caa17be1e821f5a412
• https://git.kernel.org/stable/c/b5808d40093403334d939e2c3c417144d12a6f33
• https://git.kernel.org/stable/c/d15023fb407337028a654237d8968fefdcf87c2f