setuid(2) buggy or bad docs

setuid(2) differs from the OpenBSD setuid(2) in that -EPERM is returned by the syscall even if the euid of the process matches the uid passed to it.

Either I am non compos or the thing is very wrong. The docs (man-pages-1.35) say

ERRORS
EPERM The user is not the super-user, and uid does not
match the effective or saved user ID of the calling process.

The following untested patch changes the kernel to match the documentated behaviour.

@@ -603,7 +603,9 @@ asmlinkage long sys_setuid(uid_t uid)
 		if (uid != old_ruid && set_user(uid, old_euid != uid) < 0)
 			return -EAGAIN;
 		new_suid = uid;
-	} else if ((uid != current->uid) && (uid != new_suid))
+	} else if ((uid != current->uid)
+		   && (uid != new_suid)
+		&& (uid != old_euid))
 		return -EPERM;
 
 	if (old_euid != uid)

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