netdev - [PATCH bpf-next] net: Enlarge offset check value from 0xffff to 0x7fffffff in bpf_skb_load

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Date:   Thu, 17 Mar 2022 21:59:40 +0800
From:   Liu Jian <liujian56@...wei.com>
To:     <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
        <kafai@...com>, <songliubraving@...com>, <yhs@...com>,
        <john.fastabend@...il.com>, <kpsingh@...nel.org>,
        <davem@...emloft.net>, <kuba@...nel.org>, <sdf@...gle.com>,
        <netdev@...r.kernel.org>, <bpf@...r.kernel.org>
CC:     <liujian56@...wei.com>
Subject: [PATCH bpf-next] 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: 05c74e5e53f6 ("bpf: add bpf_skb_load_bytes helper")
Signed-off-by: Liu Jian <liujian56@...wei.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 9eb785842258..236578e1b618 100644
--- a/net/core/filter.c
+++ b/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 > 0x7ffffffff || len > 0x7fffffff))
 		goto err_clear;
 
 	ptr = skb_header_pointer(skb, offset, len, to);
-- 
2.17.1