CVE-2024-36932

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

thermal/debugfs: Prevent use-after-free from occurring after cdev removal

Since thermal_debug_cdev_remove() does not run under cdev->lock, it can run in parallel with thermal_debug_cdev_state_update() and it may free the struct thermal_debugfs object used by the latter after it has been checked against NULL.

If that happens, thermal_debug_cdev_state_update() will access memory that has been freed already causing the kernel to crash.

Address this by using cdev->lock in thermal_debug_cdev_remove() around the cdev->debugfs value check (in case the same cdev is removed at the same time in two different threads) and its reset to NULL.

Cc :6.8+ stable@vger.kernel.org # 6.8+

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/c1279dee33369e2525f532364bb87207d23b9481
• https://git.kernel.org/stable/c/d351eb0ab04c3e8109895fc33250cebbce9c11da
• https://git.kernel.org/stable/c/c1279dee33369e2525f532364bb87207d23b9481
• https://git.kernel.org/stable/c/d351eb0ab04c3e8109895fc33250cebbce9c11da