Received-SPF: pass (google.com: domain of linux-kernel+bounces-161453-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
From: <shiming.cheng@mediatek.com>
To: <willemdebruijn.kernel@gmail.com>, <edumazet@google.com>,
	<davem@davemloft.net>, <kuba@kernel.org>, <pabeni@redhat.com>,
	<matthias.bgg@gmail.com>
CC: <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
	<shiming.cheng@mediatek.com>, Lena Wang <lena.wang@mediatek.com>
Subject: [PATCH net] net: drop pulled SKB_GSO_FRAGLIST skb
Date: Sun, 28 Apr 2024 22:30:10 +0800
Message-ID: <20240428143010.18719-1-shiming.cheng@mediatek.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain

From: Shiming Cheng <shiming.cheng@mediatek.com>

A SKB_GSO_FRAGLIST skb without GSO_BY_FRAGS is
expected to have all segments except the last
to be gso_size long. If this does not hold, the
skb has been modified and the fraglist gso integrity
is lost. Drop the packet, as it cannot be segmented
correctly by skb_segment_list.

The skb could be salvaged. By linearizing, dropping
the SKB_GSO_FRAGLIST bit and entering the normal
skb_segment path rather than the skb_segment_list path.

That choice is currently made in the protocol caller,
__udp_gso_segment. It's not trivial to add such a
backup path here. So let's add this backstop against
kernel crashes.

Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.")
Signed-off-by: Shiming Cheng <shiming.cheng@mediatek.com>
Signed-off-by: Lena Wang <lena.wang@mediatek.com>
---
 net/core/skbuff.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b99127712e67..4777f5fea6c3 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4491,6 +4491,7 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
 {
 	struct sk_buff *list_skb = skb_shinfo(skb)->frag_list;
 	unsigned int tnl_hlen = skb_tnl_header_len(skb);
+	unsigned int mss = skb_shinfo(skb)->gso_size;
 	unsigned int delta_truesize = 0;
 	unsigned int delta_len = 0;
 	struct sk_buff *tail = NULL;
@@ -4504,6 +4505,9 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
 	if (err)
 		goto err_linearize;
 
+	if (mss != GSO_BY_FRAGS && mss != skb_headlen(skb))
+		return ERR_PTR(-EFAULT);
+
 	skb_shinfo(skb)->frag_list = NULL;
 
 	while (list_skb) {
-- 
2.18.0