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As LDD3 chapter 6 p175 show, we can get current process UID and EUID by current->uid and current->euid. But the definition of struct task_struct of Linux Kernel 4.2 don't contain fields named by uid or euid any more. So, I wonder if there are any other methods to get UID and EUID ? Thanks!

Yang. fr
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1 Answers1

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.uid and .euid fields were moved to struct cred, which is now exposed as .cred field in struct task_struct. It was done in this commit: CRED: Separate task security context from task_struct. If you look at diff for include/linux/sched.h file, you can notice this change:

-   uid_t uid,euid,suid,fsuid;
-   gid_t gid,egid,sgid,fsgid;
+   struct cred *cred;  /* actual/objective task credentials */

So now instead of:

current->uid;
current->euid;

you should use:

const struct cred *cred = current_cred();

cred->uid;
cred->euid;

Notice that current_cred() function should be used to access .cred field, as it's RCU pointer.

Check out also check_same_owner() implementation for example.

Sam Protsenko
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    Thanks! Following your advice, I also have found some useful MACRO in ., e.g. `current_uid()`, `current_euid()` etc, to get these current process ownership information. – Yang. fr Aug 31 '16 at 04:42