From 8108a77515126f6db4374e8593956e20430307c0 Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Fri, 27 Oct 2017 09:45:34 -0700 Subject: bpf: bpf_compute_data uses incorrect cb structure SK_SKB program types use bpf_compute_data to store the end of the packet data. However, bpf_compute_data assumes the cb is stored in the qdisc layer format. But, for SK_SKB this is the wrong layer of the stack for this type. It happens to work (sort of!) because in most cases nothing happens to be overwritten today. This is very fragile and error prone. Fortunately, we have another hole in tcp_skb_cb we can use so lets put the data_end value there. Note, SK_SKB program types do not use data_meta, they are failed by sk_skb_is_valid_access(). Signed-off-by: John Fastabend Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- net/core/filter.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) (limited to 'net/core') diff --git a/net/core/filter.c b/net/core/filter.c index aa0265997f93..68eaa2f81a8e 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4243,6 +4243,31 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type, return insn - insn_buf; } +static u32 sk_skb_convert_ctx_access(enum bpf_access_type type, + const struct bpf_insn *si, + struct bpf_insn *insn_buf, + struct bpf_prog *prog, u32 *target_size) +{ + struct bpf_insn *insn = insn_buf; + int off; + + switch (si->off) { + case offsetof(struct __sk_buff, data_end): + off = si->off; + off -= offsetof(struct __sk_buff, data_end); + off += offsetof(struct sk_buff, cb); + off += offsetof(struct tcp_skb_cb, bpf.data_end); + *insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg, + si->src_reg, off); + break; + default: + return bpf_convert_ctx_access(type, si, insn_buf, prog, + target_size); + } + + return insn - insn_buf; +} + const struct bpf_verifier_ops sk_filter_prog_ops = { .get_func_proto = sk_filter_func_proto, .is_valid_access = sk_filter_is_valid_access, @@ -4301,7 +4326,7 @@ const struct bpf_verifier_ops sock_ops_prog_ops = { const struct bpf_verifier_ops sk_skb_prog_ops = { .get_func_proto = sk_skb_func_proto, .is_valid_access = sk_skb_is_valid_access, - .convert_ctx_access = bpf_convert_ctx_access, + .convert_ctx_access = sk_skb_convert_ctx_access, .gen_prologue = sk_skb_prologue, }; -- cgit v1.2.3 From bfa640757e9378c2f26867e723f1287e94f5a7ad Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Fri, 27 Oct 2017 09:45:53 -0700 Subject: bpf: rename sk_actions to align with bpf infrastructure Recent additions to support multiple programs in cgroups impose a strict requirement, "all yes is yes, any no is no". To enforce this the infrastructure requires the 'no' return code, SK_DROP in this case, to be 0. To apply these rules to SK_SKB program types the sk_actions return codes need to be adjusted. This fix adds SK_PASS and makes 'SK_DROP = 0'. Finally, remove SK_ABORTED to remove any chance that the API may allow aborted program flows to be passed up the stack. This would be incorrect behavior and allow programs to break existing policies. Signed-off-by: John Fastabend Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- net/core/filter.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/core') diff --git a/net/core/filter.c b/net/core/filter.c index 68eaa2f81a8e..6ae94f825f72 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1844,14 +1844,15 @@ BPF_CALL_4(bpf_sk_redirect_map, struct sk_buff *, skb, { struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); + /* If user passes invalid input drop the packet. */ if (unlikely(flags)) - return SK_ABORTED; + return SK_DROP; tcb->bpf.key = key; tcb->bpf.flags = flags; tcb->bpf.map = map; - return SK_REDIRECT; + return SK_PASS; } struct sock *do_sk_redirect_map(struct sk_buff *skb) -- cgit v1.2.3