kernel: ksud, core_hook: migrate ksud execution to security_bprm_check

kernel/core_hook.c

@@ -21,6 +21,7 @@
 #include <linux/uidgid.h>
 #include <linux/version.h>
 #include <linux/mount.h>
+#include <linux/binfmts.h>
 
 #include <linux/fs.h>
 #include <linux/namei.h>
@@ -684,6 +685,19 @@ __maybe_unused int ksu_kprobe_exit(void)
 	return 0;
 }
 
+static int ksu_bprm_check(struct linux_binprm *bprm)
+{
+	char *filename = (char *)bprm->filename;
+
+	if (likely(!ksu_execveat_hook))
+		return 0;
+
+	ksu_handle_pre_ksud(filename);
+
+	return 0;
+
+}
+
 static int ksu_task_prctl(int option, unsigned long arg2, unsigned long arg3,
 			  unsigned long arg4, unsigned long arg5)
 {
@@ -705,6 +719,7 @@ static int ksu_task_fix_setuid(struct cred *new, const struct cred *old,
 
 #ifndef MODULE
 static struct security_hook_list ksu_hooks[] = {
+	LSM_HOOK_INIT(bprm_check_security, ksu_bprm_check),
 	LSM_HOOK_INIT(task_prctl, ksu_task_prctl),
 	LSM_HOOK_INIT(inode_rename, ksu_inode_rename),
 	LSM_HOOK_INIT(task_fix_setuid, ksu_task_fix_setuid),

kernel/kernel_compat.c

@@ -53,7 +53,9 @@ struct file *ksu_filp_open_compat(const char *filename, int flags, umode_t mode)
 	// switch mnt_ns even if current is not wq_worker, to ensure what we open is the correct file in android mnt_ns, rather than user created mnt_ns
 	struct ksu_ns_fs_saved saved;
 	if (android_context_saved_enabled) {
+#ifdef CONFIG_KSU_DEBUG
 		pr_info("start switch current nsproxy and fs to android context\n");
+#endif
 		task_lock(current);
 		ksu_save_ns_fs(&saved);
 		ksu_load_ns_fs(&android_context_saved);
@@ -64,7 +66,9 @@ struct file *ksu_filp_open_compat(const char *filename, int flags, umode_t mode)
 		task_lock(current);
 		ksu_load_ns_fs(&saved);
 		task_unlock(current);
+#ifdef CONFIG_KSU_DEBUG
 		pr_info("switch current nsproxy and fs back to saved successfully\n");
+#endif
 	}
 	return fp;
 }
@@ -86,3 +90,4 @@ long ksu_strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
 {
 	return strncpy_from_user_nofault(dst, unsafe_addr, count);
 }
+

kernel/kernel_compat.h

@@ -32,4 +32,21 @@ extern ssize_t ksu_kernel_read_compat(struct file *p, void *buf, size_t count,
 extern ssize_t ksu_kernel_write_compat(struct file *p, const void *buf,
 				       size_t count, loff_t *pos);
 
+/*
+ * ksu_copy_from_user_retry
+ * try nofault copy first, if it fails, try with plain
+ * paramters are the same as copy_from_user
+ * 0 = success
+ */
+static long ksu_copy_from_user_retry(void *to, 
+		const void __user *from, unsigned long count)
+{
+	long ret = copy_from_user_nofault(to, from, count);
+	if (likely(!ret))
+		return ret;
+
+	// we faulted! fallback to slow path
+	return copy_from_user(to, from, count);
+}
+
 #endif