In the Linux kernel, the following vulnerability has been resolved: Input: synaptics-rmi4 - fix use after free in rmi_unregister_function() The put_device() calls rmi_release_function() which frees "fn" so the dereference on the next line "fn->num_of_irqs" is a use after free. Move the put_device() to the end to fix this.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.