macro in function argument

Question

Can you explain me this piece of code ? what does __user here mean ?

int create(struct mystruct __user *arg) {
  void __user *user_config;
}

(I only post part of the function) Any reply is much appreciated. Thank you.

Should have searched [this](http://stackoverflow.com/q/4521551/2173917)? — Sourav Ghosh, Mar 08 '16 at 20:53
you are right. Thanks a lot. I didn't know where to search :( — Tran Ngu Dang, Mar 08 '16 at 20:56
You were not able to enter `linux __user` in the google search mask? First result is the dup. If that was not offending, I'd ask if you are a politician. — too honest for this site, Mar 08 '16 at 21:01

score 2 · Accepted Answer · answered Mar 08 '16 at 20:55

2

It tells the kernel developers that the pointer is user supplied, so it shouldn't be trusted and needs to be validated before operating on.

There are many such definitions in Linux kernel.

answered Mar 08 '16 at 20:55

ronakg

Just asking, how come the dupe I pointed did not cover this? – Sourav Ghosh Mar 08 '16 at 20:57

1 Answers1