net: Enlarge offset check value from 0xffff to 0x7fffffff in bpf_skb_load_bytes

The data length of skb frags + frag_list may be greater than 0xffff,
and skb_header_pointer can not handle negative offset and negative len.
So here 0x7ffffff is used to check the validity of offset and len.

Fixes: 05c74e5 ("bpf: add bpf_skb_load_bytes helper")
Signed-off-by: Liu Jian <liujian56@huawei.com>

Author: liujian56

net/core/filter.c

@@ -1722,7 +1722,7 @@ BPF_CALL_4(bpf_skb_load_bytes, const struct sk_buff *, skb, u32, offset,
 {
 	void *ptr;
 
-	if (unlikely(offset > 0xffff))
+	if (unlikely(offset > 0x7fffffff || len > 0x7fffffff))
 		goto err_clear;
 
 	ptr = skb_header_pointer(skb, offset, len, to);