locking/csd_lock: Change csdlock_debug from early_param to __setup

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: locking/csd_lock: Change csdlock_debug from early_param to __setup The csdlock_debug kernel-boot parameter is parsed by the early_param() function csdlock_debug(). If set, csdlock_debug() invokes static_branch_enable() to enable csd_lock_wait feature, which triggers a panic on arm64 for kernels built with CONFIG_SPARSEMEM=y and CONFIG_SPARSEMEM_VMEMMAP=n. With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in static_key_enable() and returns NULL, resulting in a NULL dereference because mem_section is initialized only later in sparse_init(). This is also a problem for powerpc because early_param() functions are invoked earlier than jump_label_init(), also resulting in static_key_enable() failures. These failures cause the warning "static key 'xxx' used before call to jump_label_init()". Thus, early_param is too early for csd_lock_wait to run static_branch_enable(), so changes it to __setup to fix these.

References

• https://git.kernel.org/stable/c/d2cbdbe22b5f190055d2d0ae92e7454479343a30
• https://git.kernel.org/stable/c/05de9e2e33b1625c71aee69e353fe906dd2be88a
• https://git.kernel.org/stable/c/b480d1e9a8c11ecc1c99dc01814b28e3103bd0a0
• https://git.kernel.org/stable/c/9c9b26b0df270d4f9246e483a44686fca951a29c