Check for user = root within linux kernel?

Question

I am writing linux kernel code. I am in VFS and I want to modify it. I want to add a check to see whether or not the user is root and based on that make a decision. How do I do this? Is there a kernel version of getuid() ? Or does any structure like "current->" contain info on which user it is for the current process?

Answer 1

You can use current_cred() as defined in include/linux/cred.h, which will give you a pointer to a struct cred itself defined in the same header. Something like

  if (current_cred()->uid != 0)
     return -EPERM;