kobject: Add sanity check for kset->kobj.ktype in kset_register()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: kobject: Add sanity check for kset->kobj.ktype in kset_register() When I register a kset in the following way: static struct kset my_kset; kobject_set_name(&my_kset.kobj, "my_kset"); ret = kset_register(&my_kset); A null pointer dereference exception is occurred: [ 4453.568337] Unable to handle kernel NULL pointer dereference at \ virtual address 0000000000000028 ... ... [ 4453.810361] Call trace: [ 4453.813062] kobject_get_ownership+0xc/0x34 [ 4453.817493] kobject_add_internal+0x98/0x274 [ 4453.822005] kset_register+0x5c/0xb4 [ 4453.825820] my_kobj_init+0x44/0x1000 [my_kset] ... ... Because I didn't initialize my_kset.kobj.ktype. According to the description in Documentation/core-api/kobject.rst: - A ktype is the type of object that embeds a kobject. Every structure that embeds a kobject needs a corresponding ktype. So add sanity check to make sure kset->kobj.ktype is not NULL.

References

• https://git.kernel.org/stable/c/039ec9db2d30032eafa365f5f89b30eca5322b05
• https://git.kernel.org/stable/c/964e025ceefdf75da46b0133d0c2790de451aeec
• https://git.kernel.org/stable/c/5df5829158513134ddcaf2184d9286eda7b0bb18
• https://git.kernel.org/stable/c/f3f6bf22a4f5ba649cf26ae4670de5c7f861bdef
• https://git.kernel.org/stable/c/48aebbe801e78a8932404c122ed0e880ccedc220
• https://git.kernel.org/stable/c/1a772881bc059c596d8ca587cbd2a233edce3d3b
• https://git.kernel.org/stable/c/4d0fe8c52bb3029d83e323c961221156ab98680b