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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Domingo Dirutigliano <pwnzer0tt1@proton.me>,
        Florian Westphal <fw@strlen.de>,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 42/65] netfilter: nf_queue: do not allow packet truncation below transport header offset
Date:   Mon,  1 Aug 2022 13:46:59 +0200
Message-Id: <20220801114135.476451070@linuxfoundation.org>
In-Reply-To: <20220801114133.641770326@linuxfoundation.org>
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From: Florian Westphal <fw@strlen.de>

[ Upstream commit 99a63d36cb3ed5ca3aa6fcb64cffbeaf3b0fb164 ]

Domingo Dirutigliano and Nicola Guerrera report kernel panic when
sending nf_queue verdict with 1-byte nfta_payload attribute.

The IP/IPv6 stack pulls the IP(v6) header from the packet after the
input hook.

If user truncates the packet below the header size, this skb_pull() will
result in a malformed skb (skb->len < 0).

Fixes: 7af4cc3fa158 ("[NETFILTER]: Add "nfnetlink_queue" netfilter queue handler over nfnetlink")
Reported-by: Domingo Dirutigliano <pwnzer0tt1@proton.me>
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/netfilter/nfnetlink_queue.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 1640da5c5077..72d30922ed29 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -838,11 +838,16 @@ nfqnl_enqueue_packet(struct nf_queue_entry *entry, unsigned int queuenum)
 }
 
 static int
-nfqnl_mangle(void *data, int data_len, struct nf_queue_entry *e, int diff)
+nfqnl_mangle(void *data, unsigned int data_len, struct nf_queue_entry *e, int diff)
 {
 	struct sk_buff *nskb;
 
 	if (diff < 0) {
+		unsigned int min_len = skb_transport_offset(e->skb);
+
+		if (data_len < min_len)
+			return -EINVAL;
+
 		if (pskb_trim(e->skb, data_len))
 			return -ENOMEM;
 	} else if (diff > 0) {
-- 
2.35.1