The CWE-787 vulnerability at line 3 is due to the fact that the `len` parameter is not checked for integer overflow before being used to calculate `skb->data` and `skb->len`. This could potentially lead to a buffer overflow.

Here are five possible patches for the vulnerability:

**Patch 1: Check for integer overflow**
```c
static inline void *__skb_push(struct sk_buff *skb, unsigned int len)
{
    if (len > INT_MAX - skb->data) {
        DEBUG_NET_WARN_ON_ONCE(1);
        return NULL;
    }
    skb->data -= len;
    skb->len  += len;
    return skb->data;
}
```
This patch checks if the `len` parameter would cause an integer overflow when subtracting it from `skb->data`. If it would, the function returns `NULL`.

**Patch 2: Use a safer data type**
```c
static inline void *__skb_push(struct sk_buff *skb, size_t len)
{
    if (len > SIZE_MAX - skb->data) {
        DEBUG_NET_WARN_ON_ONCE(1);
        return NULL;
    }
    skb->data -= len;
    skb->len  += len;
    return skb->data;
}
```
This patch changes the type of the `len` parameter to `size_t`, which is an unsigned type that can represent larger values than `unsigned int`. It also checks for integer overflow using `SIZE_MAX`.

**Patch 3: Use a bounds check**
```c
static inline void *__skb_push(struct sk_buff *skb, unsigned int len)
{
    if (len > skb->end - skb->data) {
        DEBUG_NET_WARN_ON_ONCE(1);
        return NULL;
    }
    skb->data -= len;
    skb->len  += len;
    return skb->data;
}
```
This patch checks if the `len` parameter is within the bounds of the `skb` buffer. If it's not, the function returns `NULL`.

**Patch 4: Use a safer calculation**
```c
static inline void *__skb_push(struct sk_buff *skb, unsigned int len)
{
    unsigned int new_data = skb->data - len;
    if (new_data > skb->end) {
        DEBUG_NET_WARN_ON_ONCE(1);
        return NULL;
    }
    skb->data = new_data;
    skb->len  += len;
    return skb->data;
}
```
This patch calculates the new value of `skb->data` using a safer calculation that avoids integer overflow.

**Patch 5: Add a length check in the caller**
```c
static struct sk_buff *nsh_gso_segment(struct sk_buff *skb,
                                       netdev_features_t features)
{
    ...
    if (nsh_len > INT_MAX - skb->data) {
        DEBUG_NET_WARN_ON_ONCE(1);
        goto out;
    }
    __skb_push(skb, nsh_len);
    ...
}
```
This patch adds a length check in the `nsh_gso_segment` function, which calls `__skb_push`. If the length would cause an integer overflow, the function returns an error.