To generate this patch, we can follow these reasoning steps:

Step 1. Root Cause Analysis:

1. Input validation:
   - The code uses `info.rule_cnt` to determine the size of memory allocation.
   - `info.rule_cnt` is obtained from user input via `copy_from_user()`.

2. Memory allocation:
   - The vulnerable line uses `kmalloc()` to allocate memory.
   - The size of allocation is `info.rule_cnt * sizeof(u32)`.

3. Potential vulnerability:
   - `kmalloc()` allocates uninitialized memory.
   - Uninitialized memory may contain sensitive data from previous allocations.
   - If this memory is later accessed or returned to user space without proper initialization, it could lead to information leakage.

4. Vulnerability classification:
   - While labeled as CWE-787 (Out-of-bounds Write), the actual issue is more closely related to CWE-201 (Information Exposure Through Sent Data) or CWE-665 (Improper Initialization).

Step 2. Fixing Strategy:

1. The core issue is the use of uninitialized memory.
2. To fix this, we need to ensure the allocated memory is initialized.
3. Instead of `kmalloc()`, we can use `kzalloc()`, which allocates and zero-initializes memory.
4. Changing to `kzalloc()` ensures no residual data remains in the allocated buffer.

Therefore, the appropriate patch is:

```
<                 rule_buf = kmalloc(info.rule_cnt * sizeof(u32), GFP_USER);
---
>                 rule_buf = kzalloc(info.rule_cnt * sizeof(u32), GFP_USER);
```

This patch replaces `kmalloc()` with `kzalloc()`, ensuring the allocated memory is initialized to zero, thus preventing potential information leakage.