Add sanity check for iph->ihl field in nf_flow_ip4_tunnel_proto() before using it to compute the header size, avoiding out-of-bounds access with malformed IP headers. While at it, use iph->protocol instead of the hardcoded IPPROTO_IPIP constant when setting ctx->tun.proto and reference ctx->tun.hdr_size when updating ctx->offset. Fixes: ab427db178858 ("netfilter: flowtable: Add IPIP rx sw acceleration") Signed-off-by: Lorenzo Bianconi --- Changes in v2: - Roll back to pskb_may_pull() instead of using skb_header_pointer(). - Link to v1: https://lore.kernel.org/r/20260605-nf_flow_ip4_tunnel_proto-update-v1-1-9de42230f080@kernel.org --- net/netfilter/nf_flow_table_ip.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c index 9c05a50d6013..ef5d319e58d4 100644 --- a/net/netfilter/nf_flow_table_ip.c +++ b/net/netfilter/nf_flow_table_ip.c @@ -326,8 +326,10 @@ static bool nf_flow_ip4_tunnel_proto(struct nf_flowtable_ctx *ctx, return false; iph = (struct iphdr *)(skb_network_header(skb) + ctx->offset); - size = iph->ihl << 2; + if (iph->ihl < 5) + return false; + size = iph->ihl << 2; if (ip_is_fragment(iph) || unlikely(ip_has_options(size))) return false; @@ -335,9 +337,9 @@ static bool nf_flow_ip4_tunnel_proto(struct nf_flowtable_ctx *ctx, return false; if (iph->protocol == IPPROTO_IPIP) { - ctx->tun.proto = IPPROTO_IPIP; + ctx->tun.proto = iph->protocol; ctx->tun.hdr_size = size; - ctx->offset += size; + ctx->offset += ctx->tun.hdr_size; } return true; --- base-commit: 9772589b57e44aedc240211c5c3f7a684a034d3a change-id: 20260605-nf_flow_ip4_tunnel_proto-update-b31f7bff6fb9 Best regards, -- Lorenzo Bianconi