From 3eee1f75f2b9c107d4a097e8b640553376a5b171 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sat, 28 Jul 2018 00:17:56 +0200 Subject: 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") Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau --- net/core/filter.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'net') diff --git a/net/core/filter.c b/net/core/filter.c index 06da770f543f..9dfd145eedcc 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1712,24 +1712,26 @@ 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; } -- cgit v1.2.3