CVE-2023-53250: NULL Pointer Dereference

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

firmware: dmi-sysfs: Fix null-ptr-deref in dmi_sysfs_register_handle

KASAN reported a null-ptr-deref error:

KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 0 PID: 1373 Comm: modprobe Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:dmi_sysfs_entry_release ... Call Trace: <TASK> kobject_put dmi_sysfs_register_handle (drivers/firmware/dmi-sysfs.c:540) dmi_sysfs dmi_decode_table (drivers/firmware/dmi_scan.c:133) dmi_walk (drivers/firmware/dmi_scan.c:1115) dmi_sysfs_init (drivers/firmware/dmi-sysfs.c:149) dmi_sysfs do_one_initcall (init/main.c:1296) ... Kernel panic - not syncing: Fatal exception Kernel Offset: 0x4000000 from 0xffffffff81000000 ---[ end Kernel panic - not syncing: Fatal exception ]---

It is because previous patch added kobject_put() to release the memory which will call dmi_sysfs_entry_release() and list_del().

However, list_add_tail(entry->list) is called after the error block, so the list_head is uninitialized and cannot be deleted.

Move error handling to after list_add_tail to fix this.