kernel: migrate barriers to spec barriers and code style thing

overkill, but yeah, might as well move on to the real deal.

[ rsuntk: Rename original variable name ]
Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>
Signed-off-by: rsuntk <rsuntk@yukiprjkt.my.id>

kernel/core_hook.c

@@ -313,21 +313,17 @@ int ksu_handle_prctl(int option, unsigned long arg2, unsigned long arg3,
 	if (current_uid_val != manager_uid &&
 		current_uid_val % 100000 == manager_uid) {
 		ksu_set_manager_uid(current_uid_val);
-			// make sure all cpus sees this change, next line will check
-			smp_mb();
 	}
 
 skip_check:
 	// yes this causes delay, but this keeps the delay consistent, which is what we want
-	barrier();
+	// with a proper barrier for safety as the compiler and cpu might try to do something smart.
+	KCOMPAT_BARRIER();
 	if (!is_allow_su())
 		return 0;
 
 	// we move it after uid check here so they cannot
 	// compare 0xdeadbeef call to a non-0xdeadbeef call
-	// with barriers around for safety as the compiler
-	// might try to do something smart.
-	barrier();
 	if (KERNEL_SU_OPTION != option)
 		return 0;
 

kernel/kernel_compat.h

@@ -7,6 +7,14 @@
 #include "ss/policydb.h"
 #include "linux/key.h"
 
+#if defined(CONFIG_X86)
+#define KCOMPAT_BARRIER() barrier_nospec()
+#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64)
+#define KCOMPAT_BARRIER() isb() // arch/arm64/include/asm/barrier.h
+#else
+#define KCOMPAT_BARRIER() barrier() // well, compiler atleast.
+#endif
+
 /**
  * list_count_nodes - count the number of nodes in a list
  * @head: the head of the list

kernel/sucompat.c

@@ -172,8 +172,7 @@ int __ksu_handle_devpts(struct inode *inode)
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 1, 0) || defined(KSU_OPTIONAL_SELINUX_INODE)
 	struct inode_security_struct *sec = selinux_inode(inode);
 #else
-		struct inode_security_struct *sec =
+	struct inode_security_struct *sec = (struct inode_security_struct *)inode->i_security;
-			(struct inode_security_struct *)inode->i_security;
 #endif
 	if (ksu_devpts_sid && sec)
 		sec->sid = ksu_devpts_sid;