From 5f29661c628e44fa73da705a1ed55f559f0a08f5 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sat, 28 Jul 2018 00:17:56 +0200 Subject: [PATCH] bpf: fix bpf_skb_load_bytes_relative pkt length check The len > skb_headlen(skb) cannot be used as a maximum upper bound for the packet length since it does not have any relation to the full linear packet length when filtering is used from upper layers (e.g. in case of reuseport BPF programs) as by then skb->data, skb->len already got mangled through __skb_pull() and others. Fixes: 4e1ec56cdc59 ("bpf: add skb_load_bytes_relative helper") Change-Id: Ic72959d61a393dc411f7654697d39b5fabc56604 Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau --- net/core/filter.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index a81740e661f7..935374e54bdb 100755 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1513,24 +1513,26 @@ static const struct bpf_func_proto bpf_skb_load_bytes_proto = { BPF_CALL_5(bpf_skb_load_bytes_relative, const struct sk_buff *, skb, u32, offset, void *, to, u32, len, u32, start_header) { + u8 *end = skb_tail_pointer(skb); + u8 *net = skb_network_header(skb); + u8 *mac = skb_mac_header(skb); u8 *ptr; - if (unlikely(offset > 0xffff || len > skb_headlen(skb))) + if (unlikely(offset > 0xffff || len > (end - mac))) goto err_clear; switch (start_header) { case BPF_HDR_START_MAC: - ptr = skb_mac_header(skb) + offset; + ptr = mac + offset; break; case BPF_HDR_START_NET: - ptr = skb_network_header(skb) + offset; + ptr = net + offset; break; default: goto err_clear; } - if (likely(ptr >= skb_mac_header(skb) && - ptr + len <= skb_tail_pointer(skb))) { + if (likely(ptr >= mac && ptr + len <= end)) { memcpy(to, ptr, len); return 0; }