The patching can be done in two steps.

### Step 1. Root Cause Analysis: starting with input, reason about the vulnerable behavior until the vulnerability is determined:

- 1: Memory Allocation:
  - The code allocates memory for `bdev` using `kmalloc` and then for `devs` using `krealloc`.
  - If the allocation for `devs` fails, the function returns `-ENOMEM` but does not free the previously allocated memory for `bdev`.

- 2: Potential Vulnerability:
  - The vulnerability arises because the allocated memory for `bdev` is not freed when the allocation for `devs` fails.
  - This is a classic example of a memory leak. If this function is called repeatedly and the allocation for `devs` fails, the memory allocated for `bdev` will not be freed, leading to memory exhaustion.

- 3: CWE-401 (Memory Leak):
  - CWE-401 occurs when a function allocates memory but does not free it when an error occurs.
  - In this case, the memory allocated for `bdev` is not freed when the allocation for `devs` fails, resulting in a memory leak.

### Conclusion:
The vulnerable behavior in this code is a memory leak. It occurs because the memory allocated for `bdev` is not freed when the allocation for `devs` fails. To fix this vulnerability, the allocated memory for `bdev` should be freed when the allocation for `devs` fails.

### Step 2. Fixing Strategy:
A common fixing strategy is to free the allocated memory when an error occurs. In this case, the allocated memory for `bdev` should be freed when the allocation for `devs` fails. Therefore, the patch should include a call to `kfree` to free the allocated memory for `bdev` before returning `-ENOMEM`.

The patch is:
```
<                 dev_err(dev->class_dev, "Could not allocate memory. Out of memory?\n");
<                 return -ENOMEM;
---
>                 dev_err(dev->class_dev, "Could not allocate memory. Out of memory?\n");
>                 kfree(bdev);
>                 return -ENOMEM;
```
This patch ensures that the allocated memory for `bdev` is freed when the allocation for `devs` fails, preventing a memory leak.