kernel: Enhanced user data scanning

Added filesystem type checks to prevent dangerous paths

kernel/user_data_scanner.c

@@ -8,18 +8,114 @@
 #include <linux/stat.h>
 #include <linux/namei.h>
 #include <linux/sched.h>
+#include <linux/mount.h>
+#include <linux/magic.h>
+#include <linux/jiffies.h>
 
 #include "klog.h"
 #include "ksu.h"
 #include "kernel_compat.h"
 #include "user_data_scanner.h"
 
+#define KERN_PATH_TIMEOUT_MS 100
+#define MAX_FUSE_CHECK_RETRIES 3
+
 struct work_buffers *get_work_buffer(void)
 {
 	static struct work_buffers global_buffer;
 	return &global_buffer;
 }
 
+// Check the file system type
+static bool is_dangerous_fs_magic(unsigned long magic)
+{
+	switch (magic) {
+	case 0x65735546:
+	case 0x794c7630:
+	case 0x01021994:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool is_path_for_kern_path(const char *path, struct super_block *expected_sb)
+{
+	if (fatal_signal_pending(current)) {
+		pr_warn("Fatal signal pending, skip path: %s\n", path);
+		return false;
+	}
+
+	if (need_resched()) {
+		cond_resched();
+		if (fatal_signal_pending(current))
+			return false;
+	}
+
+	if (expected_sb && is_dangerous_fs_magic(expected_sb->s_magic)) {
+		pr_info("Skipping dangerous filesystem (magic=0x%lx): %s\n", 
+			expected_sb->s_magic, path);
+		return false;
+	}
+
+	if (!path || strlen(path) == 0 || strlen(path) >= PATH_MAX) {
+		return false;
+	}
+
+	if (strstr(path, ".tmp") || strstr(path, ".removing") || strstr(path, ".unmounting")) {
+		pr_debug("Path appears to be in transition state: %s\n", path);
+		return false;
+	}
+
+	return true;
+}
+
+static int kern_path_with_timeout(const char *path, unsigned int flags, struct path *result)
+{
+	unsigned long start_time = jiffies;
+	unsigned long timeout = start_time + msecs_to_jiffies(KERN_PATH_TIMEOUT_MS);
+	int retries = 0;
+	int err;
+
+	do {
+		if (time_after(jiffies, timeout)) {
+			pr_warn("kern_path timeout for: %s\n", path);
+			return -ETIMEDOUT;
+		}
+
+		if (fatal_signal_pending(current)) {
+			pr_warn("Fatal signal during kern_path: %s\n", path);
+			return -EINTR;
+		}
+
+		err = kern_path(path, flags, result);
+		
+		if (err == 0) {
+			return 0;
+		}
+
+		if (err == -ENOENT || err == -ENOTDIR || err == -EACCES) {
+			return err;
+		}
+
+		if (err == -EBUSY || err == -EAGAIN) {
+			retries++;
+			if (retries >= MAX_FUSE_CHECK_RETRIES) {
+				pr_warn("Max retries reached for: %s (err=%d)\n", path, err);
+				return err;
+			}
+			
+			usleep_range(1000, 2000);
+			continue;
+		}
+
+		return err;
+
+	} while (retries < MAX_FUSE_CHECK_RETRIES);
+
+	return err;
+}
+
 FILLDIR_RETURN_TYPE scan_user_packages(struct dir_context *ctx, const char *name,
 				       int namelen, loff_t off, u64 ino, unsigned int d_type)
 {
@@ -32,6 +128,10 @@ FILLDIR_RETURN_TYPE scan_user_packages(struct dir_context *ctx, const char *name
 	scan_ctx->processed_count++;
 	if (scan_ctx->processed_count % SCHEDULE_INTERVAL == 0) {
 		cond_resched();
+		if (fatal_signal_pending(current)) {
+			pr_info("Fatal signal received, stopping scan\n");
+			return FILLDIR_ACTOR_STOP;
+		}
 	}
 
 	if (d_type != DT_DIR || namelen <= 0)
@@ -77,17 +177,40 @@ static int process_deferred_paths(struct list_head *deferred_paths, struct list_
 {
 	struct deferred_path_info *path_info, *n;
 	int success_count = 0;
+	int skip_count = 0;
 
 	list_for_each_entry_safe(path_info, n, deferred_paths, list) {
-		struct path path;
-		int err = kern_path(path_info->path, LOOKUP_FOLLOW, &path);
-		if (err) {
-			pr_debug("Path lookup failed: %s (%d)\n", path_info->path, err);
+		if (!is_path_for_kern_path(path_info->path, NULL)) {
+			pr_debug("Skipping unsafe path: %s\n", path_info->path);
+			skip_count++;
 			list_del(&path_info->list);
 			kfree(path_info);
 			continue;
 		}
 
+		// Retrieve path information
+		struct path path;
+		int err = kern_path_with_timeout(path_info->path, LOOKUP_FOLLOW, &path);
+		if (err) {
+			if (err != -ENOENT) {
+				pr_debug("Path lookup failed: %s (%d)\n", path_info->path, err);
+			}
+			list_del(&path_info->list);
+			kfree(path_info);
+			continue;
+		}
+
+		// Check the file system type
+		if (is_dangerous_fs_magic(path.mnt->mnt_sb->s_magic)) {
+			pr_info("Skipping path on dangerous filesystem: %s (magic=0x%lx)\n", 
+				path_info->path, path.mnt->mnt_sb->s_magic);
+			path_put(&path);
+			list_del(&path_info->list);
+			kfree(path_info);
+			skip_count++;
+			continue;
+		}
+
 		struct kstat stat;
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0) || defined(KSU_HAS_NEW_VFS_GETATTR)
 		err = vfs_getattr(&path, &stat, STATX_UID, AT_STATX_SYNC_AS_STAT);
@@ -134,8 +257,16 @@ static int process_deferred_paths(struct list_head *deferred_paths, struct list_
 		
 		if (success_count % 10 == 0) {
 			cond_resched();
+			if (fatal_signal_pending(current)) {
+				pr_info("Fatal signal received, stopping path processing\n");
+				break;
 			}
 		}
+	}
+
+	if (skip_count > 0) {
+		pr_info("Skipped %d potentially dangerous paths for safety\n", skip_count);
+	}
 
 	return success_count;
 }
@@ -159,6 +290,14 @@ static int scan_primary_user_apps(struct list_head *uid_list,
 		return PTR_ERR(dir_file);
 	}
 
+	// Check the file system type
+	if (is_dangerous_fs_magic(dir_file->f_inode->i_sb->s_magic)) {
+		pr_err("Primary user path is on dangerous filesystem (magic=0x%lx), aborting\n",
+		       dir_file->f_inode->i_sb->s_magic);
+		filp_close(dir_file, NULL);
+		return -EOPNOTSUPP;
+	}
+
 	struct user_scan_ctx scan_ctx = {
 		.deferred_paths = &deferred_paths,
 		.user_id = 0,
@@ -195,6 +334,8 @@ FILLDIR_RETURN_TYPE collect_user_ids(struct dir_context *ctx, const char *name,
 	uctx->processed_count++;
 	if (uctx->processed_count % SCHEDULE_INTERVAL == 0) {
 		cond_resched();
+		if (fatal_signal_pending(current))
+			return FILLDIR_ACTOR_STOP;
 	}
 
 	if (d_type != DT_DIR || namelen <= 0)
@@ -229,6 +370,14 @@ static int get_all_active_users(struct work_buffers *work_buf, size_t *found_cou
 		return PTR_ERR(dir_file);
 	}
 
+	// Check the file system type of the base path
+	if (is_dangerous_fs_magic(dir_file->f_inode->i_sb->s_magic)) {
+		pr_err("User data base path is on dangerous filesystem (magic=0x%lx), aborting\n",
+		       dir_file->f_inode->i_sb->s_magic);
+		filp_close(dir_file, NULL);
+		return -EOPNOTSUPP;
+	}
+
 	struct user_id_ctx uctx = {
 		.ctx.actor = collect_user_ids,
 		.user_ids = work_buf->user_ids_buffer,
@@ -260,6 +409,11 @@ static int scan_secondary_users_apps(struct list_head *uid_list,
 	*total_pkg_count = *total_error_count = 0;
 
 	for (size_t i = 0; i < user_count; i++) {
+		if (fatal_signal_pending(current)) {
+			pr_info("Fatal signal received, stopping secondary user scan\n");
+			break;
+		}
+
 		// Skip the main user since it was already scanned in the first step
 		if (work_buf->user_ids_buffer[i] == 0)
 			continue;
@@ -278,6 +432,14 @@ static int scan_secondary_users_apps(struct list_head *uid_list,
 			continue;
 		}
 
+		// Check the file system type of the user directory
+		if (is_dangerous_fs_magic(dir_file->f_inode->i_sb->s_magic)) {
+			pr_info("User path %s is on dangerous filesystem (magic=0x%lx), skipping\n",
+				work_buf->path_buffer, dir_file->f_inode->i_sb->s_magic);
+			filp_close(dir_file, NULL);
+			continue;
+		}
+
 		struct user_scan_ctx scan_ctx = {
 			.deferred_paths = &deferred_paths,
 			.user_id = work_buf->user_ids_buffer[i],