Based on the provided code slice and the identified CWE-401  vulnerability at line 4, here are five possible patches to address the issue:

Patch 1:
```c
1 static inline void __free_pages(struct page *page, unsigned int order)
2 {
3 	if (pcp_allowed_order(order))		/* Via pcp? */
4 		free_unref_page(page, order);
5 	else
6 		__free_pages_ok(page, order, FPI_NONE);
7 +	page = NULL; // Set the pointer to NULL after freeing
8 }
```

Patch 2:
```c
1 static inline void __free_pages(struct page *page, unsigned int order)
2 {
3 	if (pcp_allowed_order(order))		/* Via pcp? */
4 +		if (page) {
5 +			free_unref_page(page, order);
6 +			page = NULL;
7 +		}
8 	else
9 		__free_pages_ok(page, order, FPI_NONE);
10 }
```

Patch 3:
```c
1 static inline void __free_pages(struct page *page, unsigned int order)
2 {
3 +	if (!page)
4 +		return;
5 	if (pcp_allowed_order(order))		/* Via pcp? */
6 		free_unref_page(page, order);
7 	else
8 		__free_pages_ok(page, order, FPI_NONE);
9 }
```

Patch 4:
```c
1 static inline void __free_pages(struct page *page, unsigned int order)
2 {
3 	if (pcp_allowed_order(order))		/* Via pcp? */
4 -		free_unref_page(page, order);
5 +		{
6 +			free_unref_page(page, order);
7 +			return;
8 +		}
9 	else
10 		__free_pages_ok(page, order, FPI_NONE);
11 }
```

Patch 5:
```c
1 static inline void __free_pages(struct page *page, unsigned int order)
2 {
3 +	struct page *tmp = page;
4 	if (pcp_allowed_order(order))		/* Via pcp? */
5 -		free_unref_page(page, order);
6 +		free_unref_page(tmp, order);
7 	else
8 		__free_pages_ok(page, order, FPI_NONE);
9 +	page = NULL;
10 }
```

These patches aim to prevent potential use-after-free issues by either checking for NULL pointers, setting pointers to NULL after freeing, or using temporary variables. The choice of patch depends on the specific requirements and constraints of the surrounding code.