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[2001:1c00:20d:1300:1b1c:4449:176a:89ea]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae3f6ac5fd7sm219476366b.103.2025.07.04.12.12.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Jul 2025 12:12:09 -0700 (PDT) From: Eric Woudstra To: Pablo Neira Ayuso , Jozsef Kadlecsik , Nikolay Aleksandrov , Ido Schimmel , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netfilter-devel@vger.kernel.org, bridge@lists.linux.dev, netdev@vger.kernel.org, Eric Woudstra Subject: [PATCH v13 nf-next 1/3] netfilter: utils: nf_checksum(_partial) correct data!=networkheader Date: Fri, 4 Jul 2025 21:11:33 +0200 Message-ID: <20250704191135.1815969-2-ericwouds@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250704191135.1815969-1-ericwouds@gmail.com> References: <20250704191135.1815969-1-ericwouds@gmail.com> Precedence: bulk X-Mailing-List: bridge@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In the conntrack hook it may not always be the case that: skb_network_header(skb) == skb->data. This is problematic when L4 function nf_conntrack_handle_packet() is accessing L3 data. This function uses thoff and ip_hdr() to finds it's data. But it also calculates the checksum. nf_checksum() and nf_checksum_partial() both use lower skb-checksum functions that are based on using skb->data. When skb_network_header(skb) != skb->data, adjust accordingly, so that the checksum is calculated correctly. Signed-off-by: Eric Woudstra --- net/netfilter/utils.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/net/netfilter/utils.c b/net/netfilter/utils.c index 008419db815a..daee035c25b8 100644 --- a/net/netfilter/utils.c +++ b/net/netfilter/utils.c @@ -124,16 +124,21 @@ __sum16 nf_checksum(struct sk_buff *skb, unsigned int hook, unsigned int dataoff, u8 protocol, unsigned short family) { + unsigned int nhpull = skb_network_header(skb) - skb->data; __sum16 csum = 0; + if (!pskb_may_pull(skb, nhpull)) + return -ENOMEM; + __skb_pull(skb, nhpull); switch (family) { case AF_INET: - csum = nf_ip_checksum(skb, hook, dataoff, protocol); + csum = nf_ip_checksum(skb, hook, dataoff - nhpull, protocol); break; case AF_INET6: - csum = nf_ip6_checksum(skb, hook, dataoff, protocol); + csum = nf_ip6_checksum(skb, hook, dataoff - nhpull, protocol); break; } + __skb_push(skb, nhpull); return csum; } @@ -143,18 +148,23 @@ __sum16 nf_checksum_partial(struct sk_buff *skb, unsigned int hook, unsigned int dataoff, unsigned int len, u8 protocol, unsigned short family) { + unsigned int nhpull = skb_network_header(skb) - skb->data; __sum16 csum = 0; + if (!pskb_may_pull(skb, nhpull)) + return -ENOMEM; + __skb_pull(skb, nhpull); switch (family) { case AF_INET: - csum = nf_ip_checksum_partial(skb, hook, dataoff, len, - protocol); + csum = nf_ip_checksum_partial(skb, hook, dataoff - nhpull, + len, protocol); break; case AF_INET6: - csum = nf_ip6_checksum_partial(skb, hook, dataoff, len, - protocol); + csum = nf_ip6_checksum_partial(skb, hook, dataoff - nhpull, + len, protocol); break; } + __skb_push(skb, nhpull); return csum; } -- 2.47.1