net: rfkill: gpio: Fix crash due to dereferencering uninitialized pointer

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net: rfkill: gpio: Fix crash due to dereferencering uninitialized pointer Since commit 7d5e9737efda ("net: rfkill: gpio: get the name and type from device property") rfkill_find_type() gets called with the possibly uninitialized "const char *type_name;" local variable. On x86 systems when rfkill-gpio binds to a "BCM4752" or "LNV4752" acpi_device, the rfkill->type is set based on the ACPI acpi_device_id: rfkill->type = (unsigned)id->driver_data; and there is no "type" property so device_property_read_string() will fail and leave type_name uninitialized, leading to a potential crash. rfkill_find_type() does accept a NULL pointer, fix the potential crash by initializing type_name to NULL. Note likely sofar this has not been caught because: 1. Not many x86 machines actually have a "BCM4752"/"LNV4752" acpi_device 2. The stack happened to contain NULL where type_name is stored

References

• https://git.kernel.org/stable/c/184f608a68f96794e8fe58cd5535014d53622cde
• https://git.kernel.org/stable/c/8793e7a8e1b60131a825457174ed6398111daeb7
• https://git.kernel.org/stable/c/ada2282259243387e6b6e89239aeb4897e62f051
• https://git.kernel.org/stable/c/47ade5f9d70b23a119ec20b1c6504864b2543a79
• https://git.kernel.org/stable/c/689aee35ce671aab752f159e5c8e66d7685e6887
• https://git.kernel.org/stable/c/21ba85d9d508422ca9e6698463ff9357c928c22d
• https://git.kernel.org/stable/c/21a39b958b4bcf44f7674bfbbe1bbb8cad0d842d
• https://git.kernel.org/stable/c/b6f56a44e4c1014b08859dcf04ed246500e310e5