CVE-2022-48918 in Linux
Zusammenfassung
von VulDB • 26.05.2026
To fix the NULL pointer dereference in `debugfs_dir`, we need to ensure that the pointer is validated before it is used. Based on the context of kernel development and the error trace involving module loading and debugfs, this likely occurs in a function that retrieves or uses a `debugfs_dir` pointer (e.g., from `debugfs_create_dir` or similar).
Here is the corrected code pattern. The key is to check if `debugfs_dir` is `NULL` (or an error pointer, though typically `NULL` for missing directories) before dereferencing it.
### Corrected Code Pattern
```c #include <linux/debugfs.h> #include <linux/err.h>
// ...
struct dentry *debugfs_dir; // ... (code that initializes debugfs_dir, e.g., debugfs_create_dir()) ...
// Check if debugfs_dir is NULL or an error pointer before using it if (IS_ERR_OR_NULL(debugfs_dir)) {
if (IS_ERR(debugfs_dir)) {
pr_err("Failed to create debugfs directory: %ld\n", PTR_ERR(debugfs_dir)); } else {
pr_warn("debugfs_dir is NULL, skipping debugfs operations\n"); } return PTR_ERR_OR_ZERO(debugfs_dir); }
// Now it is safe to use debugfs_dir // Example: debugfs_create_file("example", 0444, debugfs_dir, NULL, &fops); ```
### Explanation of Changes
1. **`IS_ERR_OR_NULL(debugfs_dir)`**: This macro checks if the pointer is either `NULL` or an error pointer (created by `ERR_PTR()`). This is crucial because `debugfs` functions can return error pointers on failure. 2. **`IS_ERR(debugfs_dir)`**: If it is an error pointer, we extract the error code using `PTR_ERR()` and log it. 3. **`NULL` Check**: If the pointer is `NULL`, it means the directory was not created or does not exist. We log a warning and handle it gracefully. 4. **Return Early**: If the pointer is invalid, we return an appropriate error code to prevent further execution with an invalid pointer.
### If This is in a Specific Function (e.g., `btintel` or `bluetooth` driver)
If this is related to the `btintel` or `bluetooth` modules listed in the trace, the fix might look like this in the specific driver code:
```c static int btintel_debugfs_init(struct hci_dev *hdev) {
struct btintel_data *data = hci_get_drvdata(hdev); struct dentry *debugfs_dir;
// Assume debugfs_dir is obtained here debugfs_dir = debugfs_create_dir("btintel", hdev->debugfs);
// Check for error or NULL if (IS_ERR_OR_NULL(debugfs_dir)) {
if (IS_ERR(debugfs_dir)) {
BT_ERR("Failed to create btintel debugfs directory: %ld", PTR_ERR(debugfs_dir)); return PTR_ERR(debugfs_dir); } else {
BT_WARN("debugfs_dir is NULL, skipping btintel debugfs setup"); return 0; // Or -ENODEV, depending on desired behavior } }
data->debugfs_dir = debugfs_dir;
// Now safe to create files under debugfs_dir debugfs_create_file("firmware_version", 0444, debugfs_dir, data, &btintel_fw_version_fops);
return 0; } ```
### Key Takeaway
Always validate pointers returned by kernel APIs that can fail (like `debugfs_create_*` functions) before dereferencing them. Use `IS_ERR_OR_NULL()` to handle both error pointers and `NULL` values safely.
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