kernel: add non-kprobe support for sucompat disable/enable

I have no idea if this is needed or any useful for manual fs hooks users.
Upstream, this is likely to, well, simply disable hooking of those functions,
to remove and mitigate timing issues as some detection methods can actually
differentiate these.

This is done like how vfs_read_hook, input_hook and execve_hook is disabled.
While this is not exactly the same thing, this *CAN* achieve the same results.
The complete disabling of all KernelSU hooks.

While this is probably not so useful for us, honestly, I have no idea for shit
what I am doing, but lets still port it for the sake of feature parity.

cherry pick from:
	kernel: backport support for sucompat disable/enable
	https://github.com/backslashxx/KernelSU/commit/20ffabb

Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>

kernel/sucompat.c

@@ -24,6 +24,12 @@
 #define SU_PATH "/system/bin/su"
 #define SH_PATH "/system/bin/sh"
 
+bool ksu_faccessat_hook __read_mostly = true;
+bool ksu_stat_hook __read_mostly = true;
+bool ksu_execve_sucompat_hook __read_mostly = true;
+bool ksu_execveat_sucompat_hook __read_mostly = true;
+bool ksu_devpts_hook __read_mostly = true;
+
 extern void escape_to_root();
 
 static void __user *userspace_stack_buffer(const void *d, size_t len)
@@ -54,6 +60,12 @@ int ksu_handle_faccessat(int *dfd, const char __user **filename_user, int *mode,
 {
 	const char su[] = SU_PATH;
 
+#ifndef CONFIG_KSU_WITH_KPROBES
+	if (!ksu_faccessat_hook) {
+		return 0;
+	}
+#endif
+
 	if (!ksu_is_allow_uid(current_uid().val)) {
 		return 0;
 	}
@@ -75,6 +87,12 @@ int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags)
 	// const char sh[] = SH_PATH;
 	const char su[] = SU_PATH;
 
+#ifndef CONFIG_KSU_WITH_KPROBES
+	if (!ksu_stat_hook){
+		return 0;
+	}
+#endif
+
 	if (!ksu_is_allow_uid(current_uid().val)) {
 		return 0;
 	}
@@ -119,6 +137,12 @@ int ksu_handle_execveat_sucompat(int *fd, struct filename **filename_ptr,
 	const char sh[] = KSUD_PATH;
 	const char su[] = SU_PATH;
 
+#ifndef CONFIG_KSU_WITH_KPROBES
+	if (!ksu_execveat_sucompat_hook) {
+		return 0;
+	}
+#endif
+
 	if (unlikely(!filename_ptr))
 		return 0;
 
@@ -148,6 +172,12 @@ int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
 	const char su[] = SU_PATH;
 	char path[sizeof(su) + 1];
 
+#ifndef CONFIG_KSU_WITH_KPROBES
+	if (!ksu_execve_sucompat_hook) {
+		return 0;
+	}
+#endif
+
 	if (unlikely(!filename_user))
 		return 0;
 
@@ -170,6 +200,12 @@ int ksu_handle_execve_sucompat(int *fd, const char __user **filename_user,
 
 int ksu_handle_devpts(struct inode *inode)
 {
+#ifndef CONFIG_KSU_WITH_KPROBES
+	if (!ksu_devpts_hook) {
+		return 0;
+	}
+#endif
+
 	if (!current->mm) {
 		return 0;
 	}
@@ -244,35 +280,39 @@ static int pts_unix98_lookup_pre(struct kprobe *p, struct pt_regs *regs)
 
 	return ksu_handle_devpts(inode);
 }
-#endif
 
 static struct kprobe *init_kprobe(const char *name,
-	kprobe_pre_handler_t handler)
+				  kprobe_pre_handler_t handler)
 {
-struct kprobe *kp = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
-if (!kp)
-return NULL;
-kp->symbol_name = name;
-kp->pre_handler = handler;
-int ret = register_kprobe(kp);
-pr_info("sucompat: register_%s kprobe: %d\n", name, ret);
-if (ret) {
-kfree(kp);
-return NULL;
-}
-return kp;
+	struct kprobe *kp = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
+	if (!kp)
+		return NULL;
+	kp->symbol_name = name;
+	kp->pre_handler = handler;
+
+	int ret = register_kprobe(kp);
+	pr_info("sucompat: register_%s kprobe: %d\n", name, ret);
+	if (ret) {
+		kfree(kp);
+		return NULL;
+	}
+
+	return kp;
 }
+
 static void destroy_kprobe(struct kprobe **kp_ptr)
 {
-struct kprobe *kp = *kp_ptr;
-if (!kp)
-return;
-unregister_kprobe(kp);
-synchronize_rcu();
-kfree(kp);
-*kp_ptr = NULL;
+	struct kprobe *kp = *kp_ptr;
+	if (!kp)
+		return;
+	unregister_kprobe(kp);
+	synchronize_rcu();
+	kfree(kp);
+	*kp_ptr = NULL;
 }
+
 static struct kprobe *su_kps[4];
+#endif
 
 // sucompat: permited process can execute 'su' to gain root access.
 void ksu_sucompat_init()
@@ -282,6 +322,13 @@ void ksu_sucompat_init()
 	su_kps[1] = init_kprobe(SYS_FACCESSAT_SYMBOL, faccessat_handler_pre);
 	su_kps[2] = init_kprobe(SYS_NEWFSTATAT_SYMBOL, newfstatat_handler_pre);
 	su_kps[3] = init_kprobe("pts_unix98_lookup", pts_unix98_lookup_pre);
+#else
+	ksu_faccessat_hook = true;
+	ksu_stat_hook = true;
+	ksu_execve_sucompat_hook = true;
+	ksu_execveat_sucompat_hook = true;
+	ksu_devpts_hook = true;
+	pr_info("ksu_sucompat_init: hooks enabled: execve/execveat_su, faccessat, stat, devpts\n");
 #endif
 }
 
@@ -291,5 +338,12 @@ void ksu_sucompat_exit()
 	for (int i = 0; i < ARRAY_SIZE(su_kps); i++) {
 		destroy_kprobe(&su_kps[i]);
 	}
+#else
+	ksu_faccessat_hook = false;
+	ksu_stat_hook = false;
+	ksu_execve_sucompat_hook = false;
+	ksu_execveat_sucompat_hook = false;
+	ksu_devpts_hook = false;
+	pr_info("ksu_sucompat_exit: hooks disabled: execve/execveat_su, faccessat, stat, devpts\n");
 #endif
 }