From: Yizhou Zhao Date: Mon, 11 May 2026 17:30:41 +0000 (+0800) Subject: netfilter: nft_inner: Fix IPv6 inner_thoff desync X-Git-Tag: v7.1-rc5~40^2~55^2~8 X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=b6a91f68ebfed9c38e0e9150f58a9b85da07181c;p=thirdparty%2Fkernel%2Flinux.git netfilter: nft_inner: Fix IPv6 inner_thoff desync In nft_inner_parse_l2l3(), when processing inner IPv6 packets, ipv6_find_hdr() correctly computes the transport header offset traversing all extension headers, but the result is immediately overwritten with nhoff + sizeof(_ip6h) (40 bytes), which only accounts for the IPv6 base header. This creates a desync between inner_thoff (wrong — points to extension header start) and l4proto (correct — e.g., IPPROTO_TCP), enabling transport header forgery and potential firewall bypass. This issue affects stable versions from Linux 6.2. For comparison, the normal (non-inner) IPv6 path correctly preserves ipv6_find_hdr()'s result. Removing the incorrect overwrite ensures that ipv6_find_hdr()'s calculated transport header offset is preserved, thereby fixing the desynchronization. Fixes: 3a07327d10a0 ("netfilter: nft_inner: support for inner tunnel header matching") Cc: stable@vger.kernel.org Reported-by: Yizhou Zhao Reported-by: Yuxiang Yang Reported-by: Xuewei Feng Reported-by: Qi Li Reported-by: Ke Xu Assisted-by: GLM:5.1 Z.ai Signed-off-by: Yizhou Zhao Reviewed-by: Fernando Fernandez Mancera Signed-off-by: Pablo Neira Ayuso --- diff --git a/net/netfilter/nft_inner.c b/net/netfilter/nft_inner.c index 03ffb1159fc18..859aa38e333b8 100644 --- a/net/netfilter/nft_inner.c +++ b/net/netfilter/nft_inner.c @@ -163,7 +163,6 @@ static int nft_inner_parse_l2l3(const struct nft_inner *priv, return -1; if (fragoff == 0) { - thoff = nhoff + sizeof(_ip6h); ctx->flags |= NFT_PAYLOAD_CTX_INNER_TH; ctx->inner_thoff = thoff; ctx->l4proto = l4proto;