From 34f79502bbcfab659b8729da68b5e387f96eb4c1 Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Wed, 18 Oct 2017 07:10:36 -0700 Subject: bpf: avoid preempt enable/disable in sockmap using tcp_skb_cb region SK_SKB BPF programs are run from the socket/tcp context but early in the stack before much of the TCP metadata is needed in tcp_skb_cb. So we can use some unused fields to place BPF metadata needed for SK_SKB programs when implementing the redirect function. This allows us to drop the preempt disable logic. It does however require an API change so sk_redirect_map() has been updated to additionally provide ctx_ptr to skb. Note, we do however continue to disable/enable preemption around actual BPF program running to account for map updates. Signed-off-by: John Fastabend Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- include/net/tcp.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/net/tcp.h') diff --git a/include/net/tcp.h b/include/net/tcp.h index 89974c5286d8..b1ef98ebce53 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -840,6 +840,11 @@ struct tcp_skb_cb { struct inet6_skb_parm h6; #endif } header; /* For incoming skbs */ + struct { + __u32 key; + __u32 flags; + struct bpf_map *map; + } bpf; }; }; -- cgit v1.2.3 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 --- include/net/tcp.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/net/tcp.h') diff --git a/include/net/tcp.h b/include/net/tcp.h index b1ef98ebce53..33599d17522d 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -844,6 +844,7 @@ struct tcp_skb_cb { __u32 key; __u32 flags; struct bpf_map *map; + void *data_end; } bpf; }; }; -- cgit v1.2.3 From 2b7cda9c35d3b940eb9ce74b30bbd5eb30db493d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 30 Oct 2017 23:08:20 -0700 Subject: tcp: fix tcp_mtu_probe() vs highest_sack Based on SNMP values provided by Roman, Yuchung made the observation that some crashes in tcp_sacktag_walk() might be caused by MTU probing. Looking at tcp_mtu_probe(), I found that when a new skb was placed in front of the write queue, we were not updating tcp highest sack. If one skb is freed because all its content was copied to the new skb (for MTU probing), then tp->highest_sack could point to a now freed skb. Bad things would then happen, including infinite loops. This patch renames tcp_highest_sack_combine() and uses it from tcp_mtu_probe() to fix the bug. Note that I also removed one test against tp->sacked_out, since we want to replace tp->highest_sack regardless of whatever condition, since keeping a stale pointer to freed skb is a recipe for disaster. Fixes: a47e5a988a57 ("[TCP]: Convert highest_sack to sk_buff to allow direct access") Signed-off-by: Eric Dumazet Reported-by: Alexei Starovoitov Reported-by: Roman Gushchin Reported-by: Oleksandr Natalenko Acked-by: Alexei Starovoitov Acked-by: Neal Cardwell Acked-by: Yuchung Cheng Signed-off-by: David S. Miller --- include/net/tcp.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/net/tcp.h') diff --git a/include/net/tcp.h b/include/net/tcp.h index 33599d17522d..e6d0002a1b0b 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1771,12 +1771,12 @@ static inline void tcp_highest_sack_reset(struct sock *sk) tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk); } -/* Called when old skb is about to be deleted (to be combined with new skb) */ -static inline void tcp_highest_sack_combine(struct sock *sk, +/* Called when old skb is about to be deleted and replaced by new skb */ +static inline void tcp_highest_sack_replace(struct sock *sk, struct sk_buff *old, struct sk_buff *new) { - if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack)) + if (old == tcp_highest_sack(sk)) tcp_sk(sk)->highest_sack = new; } -- cgit v1.2.3