clk: Fix clk_hw_get_clk() when dev is NULL

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: clk: Fix clk_hw_get_clk() when dev is NULL Any registered clk_core structure can have a NULL pointer in its dev field. While never actually documented, this is evidenced by the wide usage of clk_register and clk_hw_register with a NULL device pointer, and the fact that the core of_clk_hw_register() function also passes a NULL device pointer. A call to clk_hw_get_clk() on a clk_hw struct whose clk_core is in that case will result in a NULL pointer derefence when it calls dev_name() on that NULL device pointer. Add a test for this case and use NULL as the dev_id if the device pointer is NULL.

References

• https://git.kernel.org/stable/c/4be3e4c05d8dd1b83b75652cad88c9e752ec7054
• https://git.kernel.org/stable/c/d183f20cf5a7b546d4108e796b98210ceb317579
• https://git.kernel.org/stable/c/23f89fe005b105f0dcc55034c13eb89f9b570fac
• https://git.kernel.org/stable/c/0c1b56df451716ba207bbf59f303473643eee4fd