| Message ID | 20230720-so-reuseport-v6-7-7021b683cdae@isovalent.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add SO_REUSEPORT support for TC bpf_sk_assign | expand |
From: Lorenz Bauer <lmb@isovalent.com> Date: Thu, 20 Jul 2023 17:30:11 +0200 > Currently the bpf_sk_assign helper in tc BPF context refuses SO_REUSEPORT > sockets. This means we can't use the helper to steer traffic to Envoy, > which configures SO_REUSEPORT on its sockets. In turn, we're blocked > from removing TPROXY from our setup. > > The reason that bpf_sk_assign refuses such sockets is that the > bpf_sk_lookup helpers don't execute SK_REUSEPORT programs. Instead, > one of the reuseport sockets is selected by hash. This could cause > dispatch to the "wrong" socket: > > sk = bpf_sk_lookup_tcp(...) // select SO_REUSEPORT by hash > bpf_sk_assign(skb, sk) // SK_REUSEPORT wasn't executed > > Fixing this isn't as simple as invoking SK_REUSEPORT from the lookup > helpers unfortunately. In the tc context, L2 headers are at the start > of the skb, while SK_REUSEPORT expects L3 headers instead. > > Instead, we execute the SK_REUSEPORT program when the assigned socket > is pulled out of the skb, further up the stack. This creates some > trickiness with regards to refcounting as bpf_sk_assign will put both > refcounted and RCU freed sockets in skb->sk. reuseport sockets are RCU > freed. We can infer that the sk_assigned socket is RCU freed if the > reuseport lookup succeeds, but convincing yourself of this fact isn't > straight forward. Therefore we defensively check refcounting on the > sk_assign sock even though it's probably not required in practice. > > Fixes: 8e368dc72e86 ("bpf: Fix use of sk->sk_reuseport from sk_assign") > Fixes: cf7fbe660f2d ("bpf: Add socket assign support") > Co-developed-by: Daniel Borkmann <daniel@iogearbox.net> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> > Cc: Joe Stringer <joe@cilium.io> > Link: https://lore.kernel.org/bpf/CACAyw98+qycmpQzKupquhkxbvWK4OFyDuuLMBNROnfWMZxUWeA@mail.gmail.com/ > Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> > Signed-off-by: Lorenz Bauer <lmb@isovalent.com> > --- > include/net/inet6_hashtables.h | 56 ++++++++++++++++++++++++++++++++++++++---- > include/net/inet_hashtables.h | 49 ++++++++++++++++++++++++++++++++++-- > include/net/sock.h | 7 ++++-- > include/uapi/linux/bpf.h | 3 --- > net/core/filter.c | 2 -- > net/ipv4/udp.c | 8 ++++-- > net/ipv6/udp.c | 10 +++++--- > tools/include/uapi/linux/bpf.h | 3 --- > 8 files changed, 116 insertions(+), 22 deletions(-) > > diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h > index a6722d6ef80f..284b5ce7205d 100644 > --- a/include/net/inet6_hashtables.h > +++ b/include/net/inet6_hashtables.h > @@ -103,6 +103,46 @@ static inline struct sock *__inet6_lookup(struct net *net, > daddr, hnum, dif, sdif); > } > > +static inline > +struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff, > + const struct in6_addr *saddr, const __be16 sport, > + const struct in6_addr *daddr, const __be16 dport, > + bool *refcounted, inet6_ehashfn_t *ehashfn) > +{ > + struct sock *sk, *reuse_sk; > + bool prefetched; > + > + sk = skb_steal_sock(skb, refcounted, &prefetched); > + if (!sk) > + return NULL; > + > + if (!prefetched) > + return sk; > + > + if (sk->sk_protocol == IPPROTO_TCP) { > + if (sk->sk_state != TCP_LISTEN) > + return sk; > + } else if (sk->sk_protocol == IPPROTO_UDP) { > + if (sk->sk_state != TCP_CLOSE) > + return sk; > + } else { > + return sk; > + } > + > + reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, > + saddr, sport, daddr, ntohs(dport), > + ehashfn); > + if (!reuse_sk) > + return sk; > + > + /* We've chosen a new reuseport sock which is never refcounted. This > + * implies that sk also isn't refcounted. > + */ > + WARN_ON_ONCE(*refcounted); > + > + return reuse_sk; > +} > + > static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, > struct sk_buff *skb, int doff, > const __be16 sport, > @@ -110,14 +150,20 @@ static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, > int iif, int sdif, > bool *refcounted) > { > - struct sock *sk = skb_steal_sock(skb, refcounted); > - > + struct net *net = dev_net(skb_dst(skb)->dev); > + const struct ipv6hdr *ip6h = ipv6_hdr(skb); > + struct sock *sk; > + > + sk = inet6_steal_sock(net, skb, doff, &ip6h->saddr, sport, &ip6h->daddr, dport, > + refcounted, inet6_ehashfn); > + if (IS_ERR(sk)) > + return NULL; > if (sk) > return sk; > > - return __inet6_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, > - doff, &ipv6_hdr(skb)->saddr, sport, > - &ipv6_hdr(skb)->daddr, ntohs(dport), > + return __inet6_lookup(net, hashinfo, skb, > + doff, &ip6h->saddr, sport, > + &ip6h->daddr, ntohs(dport), > iif, sdif, refcounted); > } > > diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h > index c0532cc7587f..1177effabed3 100644 > --- a/include/net/inet_hashtables.h > +++ b/include/net/inet_hashtables.h > @@ -449,6 +449,46 @@ static inline struct sock *inet_lookup(struct net *net, > return sk; > } > > +static inline > +struct sock *inet_steal_sock(struct net *net, struct sk_buff *skb, int doff, > + const __be32 saddr, const __be16 sport, > + const __be32 daddr, const __be16 dport, > + bool *refcounted, inet_ehashfn_t *ehashfn) > +{ > + struct sock *sk, *reuse_sk; > + bool prefetched; > + > + sk = skb_steal_sock(skb, refcounted, &prefetched); > + if (!sk) > + return NULL; > + > + if (!prefetched) > + return sk; > + > + if (sk->sk_protocol == IPPROTO_TCP) { > + if (sk->sk_state != TCP_LISTEN) > + return sk; > + } else if (sk->sk_protocol == IPPROTO_UDP) { > + if (sk->sk_state != TCP_CLOSE) > + return sk; > + } else { > + return sk; > + } > + > + reuse_sk = inet_lookup_reuseport(net, sk, skb, doff, > + saddr, sport, daddr, ntohs(dport), > + ehashfn); > + if (!reuse_sk) > + return sk; > + > + /* We've chosen a new reuseport sock which is never refcounted. This > + * implies that sk also isn't refcounted. > + */ > + WARN_ON_ONCE(*refcounted); > + > + return reuse_sk; > +} > + > static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, > struct sk_buff *skb, > int doff, > @@ -457,13 +497,18 @@ static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, > const int sdif, > bool *refcounted) > { > - struct sock *sk = skb_steal_sock(skb, refcounted); > + struct net *net = dev_net(skb_dst(skb)->dev); > const struct iphdr *iph = ip_hdr(skb); > + struct sock *sk; > > + sk = inet_steal_sock(net, skb, doff, iph->saddr, sport, iph->daddr, dport, > + refcounted, inet_ehashfn); > + if (IS_ERR(sk)) > + return NULL; > if (sk) > return sk; > > - return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, > + return __inet_lookup(net, hashinfo, skb, > doff, iph->saddr, sport, > iph->daddr, dport, inet_iif(skb), sdif, > refcounted); > diff --git a/include/net/sock.h b/include/net/sock.h > index 2eb916d1ff64..320f00e69ae9 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -2814,20 +2814,23 @@ sk_is_refcounted(struct sock *sk) > * skb_steal_sock - steal a socket from an sk_buff > * @skb: sk_buff to steal the socket from > * @refcounted: is set to true if the socket is reference-counted > + * @prefetched: is set to true if the socket was assigned from bpf > */ > static inline struct sock * > -skb_steal_sock(struct sk_buff *skb, bool *refcounted) > +skb_steal_sock(struct sk_buff *skb, bool *refcounted, bool *prefetched) > { > if (skb->sk) { > struct sock *sk = skb->sk; > > *refcounted = true; > - if (skb_sk_is_prefetched(skb)) > + *prefetched = skb_sk_is_prefetched(skb); > + if (*prefetched) > *refcounted = sk_is_refcounted(sk); > skb->destructor = NULL; > skb->sk = NULL; > return sk; > } > + *prefetched = false; > *refcounted = false; > return NULL; > } > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 739c15906a65..7fc98f4b63e9 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -4198,9 +4198,6 @@ union bpf_attr { > * **-EOPNOTSUPP** if the operation is not supported, for example > * a call from outside of TC ingress. > * > - * **-ESOCKTNOSUPPORT** if the socket type is not supported > - * (reuseport). > - * > * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) > * Description > * Helper is overloaded depending on BPF program type. This > diff --git a/net/core/filter.c b/net/core/filter.c > index b5b51ef48c5f..7c37f4646c20 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -7351,8 +7351,6 @@ BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) > return -EOPNOTSUPP; > if (unlikely(dev_net(skb->dev) != sock_net(sk))) > return -ENETUNREACH; > - if (unlikely(sk_fullsock(sk) && sk->sk_reuseport)) > - return -ESOCKTNOSUPPORT; > if (sk_unhashed(sk)) > return -EOPNOTSUPP; > if (sk_is_refcounted(sk) && > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > index 045eca6ed177..ec1a5f8a2eca 100644 > --- a/net/ipv4/udp.c > +++ b/net/ipv4/udp.c > @@ -2388,7 +2388,11 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > if (udp4_csum_init(skb, uh, proto)) > goto csum_error; > > - sk = skb_steal_sock(skb, &refcounted); > + sk = inet_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, > + &refcounted, udp_ehashfn); > + if (IS_ERR(sk)) > + goto no_sk; > + > if (sk) { > struct dst_entry *dst = skb_dst(skb); > int ret; > @@ -2409,7 +2413,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, udptable); > if (sk) > return udp_unicast_rcv_skb(sk, skb, uh); > - > +no_sk: > if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) > goto drop; > nf_reset_ct(skb); > diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c > index 109f14b17a09..f6fc75edfa23 100644 > --- a/net/ipv6/udp.c > +++ b/net/ipv6/udp.c > @@ -925,9 +925,9 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; > const struct in6_addr *saddr, *daddr; > struct net *net = dev_net(skb->dev); > + bool refcounted; > struct udphdr *uh; > struct sock *sk; > - bool refcounted; > u32 ulen = 0; > > if (!pskb_may_pull(skb, sizeof(struct udphdr))) This chunk is unnecessary. If there is no other comments from anyone, it would be good to drop this while merging. Thanks! > @@ -964,7 +964,11 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > goto csum_error; > > /* Check if the socket is already available, e.g. due to early demux */ > - sk = skb_steal_sock(skb, &refcounted); > + sk = inet6_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, > + &refcounted, udp6_ehashfn); > + if (IS_ERR(sk)) > + goto no_sk; > + > if (sk) { > struct dst_entry *dst = skb_dst(skb); > int ret; > @@ -998,7 +1002,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > goto report_csum_error; > return udp6_unicast_rcv_skb(sk, skb, uh); > } > - > +no_sk: > reason = SKB_DROP_REASON_NO_SOCKET; > > if (!uh->check) > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > index 739c15906a65..7fc98f4b63e9 100644 > --- a/tools/include/uapi/linux/bpf.h > +++ b/tools/include/uapi/linux/bpf.h > @@ -4198,9 +4198,6 @@ union bpf_attr { > * **-EOPNOTSUPP** if the operation is not supported, for example > * a call from outside of TC ingress. > * > - * **-ESOCKTNOSUPPORT** if the socket type is not supported > - * (reuseport). > - * > * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) > * Description > * Helper is overloaded depending on BPF program type. This > > -- > 2.41.0
On Thu, 20 Jul 2023 at 21:04, Lorenz Bauer <lmb@isovalent.com> wrote: > > Currently the bpf_sk_assign helper in tc BPF context refuses SO_REUSEPORT > sockets. This means we can't use the helper to steer traffic to Envoy, > which configures SO_REUSEPORT on its sockets. In turn, we're blocked > from removing TPROXY from our setup. > > The reason that bpf_sk_assign refuses such sockets is that the > bpf_sk_lookup helpers don't execute SK_REUSEPORT programs. Instead, > one of the reuseport sockets is selected by hash. This could cause > dispatch to the "wrong" socket: > > sk = bpf_sk_lookup_tcp(...) // select SO_REUSEPORT by hash > bpf_sk_assign(skb, sk) // SK_REUSEPORT wasn't executed > > Fixing this isn't as simple as invoking SK_REUSEPORT from the lookup > helpers unfortunately. In the tc context, L2 headers are at the start > of the skb, while SK_REUSEPORT expects L3 headers instead. > > Instead, we execute the SK_REUSEPORT program when the assigned socket > is pulled out of the skb, further up the stack. This creates some > trickiness with regards to refcounting as bpf_sk_assign will put both > refcounted and RCU freed sockets in skb->sk. reuseport sockets are RCU > freed. We can infer that the sk_assigned socket is RCU freed if the > reuseport lookup succeeds, but convincing yourself of this fact isn't > straight forward. Therefore we defensively check refcounting on the > sk_assign sock even though it's probably not required in practice. > > Fixes: 8e368dc72e86 ("bpf: Fix use of sk->sk_reuseport from sk_assign") > Fixes: cf7fbe660f2d ("bpf: Add socket assign support") > Co-developed-by: Daniel Borkmann <daniel@iogearbox.net> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> > Cc: Joe Stringer <joe@cilium.io> > Link: https://lore.kernel.org/bpf/CACAyw98+qycmpQzKupquhkxbvWK4OFyDuuLMBNROnfWMZxUWeA@mail.gmail.com/ > Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> > Signed-off-by: Lorenz Bauer <lmb@isovalent.com> > --- Hi Lorenz, Kuniyuki, Martin, I am getting a KASAN (inline mode) splat on bpf-next when I run ./test_progs -t btf_skc_cls_ingress, and I bisected it to this commit: 9c02bec95954 ("bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign") bash-5.2# ./test_progs -t btf_skc_cls_ingress [ 51.611015] bpf_testmod: loading out-of-tree module taints kernel. [ 51.611434] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel [ 51.809645] ================================================================== [ 51.810085] BUG: KASAN: slab-out-of-bounds in tcp_v6_rcv+0x2d7d/0x3440 [ 51.810458] Read of size 2 at addr ffff8881053f038c by task test_progs/226 [ 51.810848] [ 51.810955] CPU: 4 PID: 226 Comm: test_progs Tainted: G OE 6.5.0-rc2-g9c02bec95954 #51 [ 51.811467] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-2.fc39 04/01/2014 [ 51.811968] Call Trace: [ 51.812118] <IRQ> [ 51.812239] dump_stack_lvl+0x4a/0x80 [ 51.812452] print_report+0xcf/0x670 [ 51.812660] ? __pfx___lock_acquire+0x10/0x10 [ 51.812930] kasan_report+0xda/0x110 [ 51.813140] ? tcp_v6_rcv+0x2d7d/0x3440 [ 51.813363] ? tcp_v6_rcv+0x2d7d/0x3440 [ 51.813585] tcp_v6_rcv+0x2d7d/0x3440 [ 51.813808] ? __pfx_tcp_v6_rcv+0x10/0x10 [ 51.814051] ? __pfx_raw6_local_deliver+0x10/0x10 [ 51.814322] ? lock_acquire+0x18e/0x4b0 [ 51.814543] ? ip6_input_finish+0xda/0x240 [ 51.814783] ip6_protocol_deliver_rcu+0x12a/0x1310 [ 51.815067] ? find_held_lock+0x2d/0x110 [ 51.815293] ip6_input_finish+0x118/0x240 [ 51.815526] ? __pfx_lock_release+0x10/0x10 [ 51.815770] ip6_input+0xc4/0x300 [ 51.815972] ? __pfx_ip6_input+0x10/0x10 [ 51.816204] ? ip6_rcv_core+0x996/0x1990 [ 51.816431] ipv6_rcv+0x3bf/0x780 [ 51.816625] ? __pfx_ipv6_rcv+0x10/0x10 [ 51.816853] ? lock_acquire+0x18e/0x4b0 [ 51.817088] ? process_backlog+0x1d8/0x620 [ 51.817325] ? __pfx_ipv6_rcv+0x10/0x10 [ 51.817546] __netif_receive_skb_one_core+0x11a/0x1b0 [ 51.817837] ? __pfx___netif_receive_skb_one_core+0x10/0x10 [ 51.818166] ? mark_held_locks+0x94/0xe0 [ 51.818392] process_backlog+0xd3/0x620 [ 51.818614] __napi_poll.constprop.0+0xa3/0x540 [ 51.818890] net_rx_action+0x3b4/0xa80 [ 51.819113] ? __pfx_net_rx_action+0x10/0x10 [ 51.819365] ? reacquire_held_locks+0x490/0x4b0 [ 51.819631] __do_softirq+0x202/0x83f [ 51.819852] ? __pfx___do_softirq+0x10/0x10 [ 51.820103] ? tick_nohz_stop_idle+0x19e/0x280 [ 51.820360] ? __dev_queue_xmit+0x818/0x2d50 [ 51.820608] do_softirq+0x47/0xa0 [ 51.820817] </IRQ> [ 51.820954] <TASK> [ 51.821080] __local_bh_enable_ip+0xf2/0x120 [ 51.821324] __dev_queue_xmit+0x83c/0x2d50 [ 51.821561] ? __pfx_mark_lock+0x10/0x10 [ 51.821795] ? __pfx___dev_queue_xmit+0x10/0x10 [ 51.822064] ? lock_acquire+0x18e/0x4b0 [ 51.822285] ? find_held_lock+0x2d/0x110 [ 51.822511] ? lock_release+0x1de/0x620 [ 51.822737] ? ip6_finish_output+0x666/0x1250 [ 51.822998] ? __pfx_lock_release+0x10/0x10 [ 51.823238] ? mark_held_locks+0x94/0xe0 [ 51.823467] ip6_finish_output2+0xd8d/0x1bb0 [ 51.823717] ? ip6_mtu+0x13f/0x350 [ 51.823928] ? __pfx_ip6_finish_output2+0x10/0x10 [ 51.824195] ? find_held_lock+0x2d/0x110 [ 51.824427] ? lock_release+0x1de/0x620 [ 51.824650] ip6_finish_output+0x666/0x1250 [ 51.824906] ip6_output+0x1ed/0x6c0 [ 51.825113] ? __pfx_ip6_output+0x10/0x10 [ 51.825343] ? ip6_xmit+0xed5/0x1f40 [ 51.825551] ? __pfx_ip6_finish_output+0x10/0x10 [ 51.825821] ? nf_hook_slow+0xa9/0x180 [ 51.826048] ip6_xmit+0xbd2/0x1f40 [ 51.826248] ? lock_acquire+0x181/0x4b0 [ 51.826470] ? __pfx_ip6_xmit+0x10/0x10 [ 51.826696] ? __pfx_dst_output+0x10/0x10 [ 51.826937] ? __pfx_lock_acquire+0x10/0x10 [ 51.827176] ? release_sock+0x53/0x180 [ 51.827393] ? __pfx_inet6_csk_route_socket+0x10/0x10 [ 51.827684] ? entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 51.827993] inet6_csk_xmit+0x31c/0x570 [ 51.828215] ? __pfx_inet6_csk_xmit+0x10/0x10 [ 51.828467] __tcp_transmit_skb+0x1708/0x3630 [ 51.828732] ? __pfx___tcp_transmit_skb+0x10/0x10 [ 51.829017] ? __alloc_skb+0x110/0x280 [ 51.829238] ? __pfx___alloc_skb+0x10/0x10 [ 51.829474] ? __tcp_send_ack.part.0+0x64/0x590 [ 51.829743] tcp_rcv_state_process+0xeba/0x4ff0 [ 51.830015] ? __pfx_tcp_rcv_state_process+0x10/0x10 [ 51.830298] ? __pfx_mark_lock+0x10/0x10 [ 51.830524] ? find_held_lock+0x2d/0x110 [ 51.830756] ? lock_release+0x1de/0x620 [ 51.830988] ? __release_sock+0xd8/0x2b0 [ 51.831215] ? tcp_v6_do_rcv+0x34e/0x13a0 [ 51.831443] tcp_v6_do_rcv+0x34e/0x13a0 [ 51.831665] ? __local_bh_enable_ip+0xa6/0x120 [ 51.831935] __release_sock+0x12c/0x2b0 [ 51.832158] release_sock+0x53/0x180 [ 51.832365] __inet_stream_connect+0x6a2/0x1100 [ 51.832634] ? __pfx___inet_stream_connect+0x10/0x10 [ 51.832934] ? __pfx_woken_wake_function+0x10/0x10 [ 51.833209] ? lockdep_hardirqs_on_prepare+0x27b/0x3f0 [ 51.833501] inet_stream_connect+0x57/0xa0 [ 51.833743] __sys_connect+0x106/0x130 [ 51.833973] ? __sys_setsockopt+0x19d/0x410 [ 51.834211] ? __pfx___sys_connect+0x10/0x10 [ 51.834460] ? __pfx_blkcg_maybe_throttle_current+0x10/0x10 [ 51.834780] __x64_sys_connect+0x72/0xb0 [ 51.835019] ? syscall_enter_from_user_mode+0x20/0x50 [ 51.835312] do_syscall_64+0x3c/0x90 [ 51.835523] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 51.835818] RIP: 0033:0x7f99941965b4 [ 51.836034] Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d b5 8d 12 00 00 74 13 b8 2a 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 4c c3 0f 1f 00 55 48 89 e5 48 83 ec 10 89 55 [ 51.837071] RSP: 002b:00007ffc9a4a3ea8 EFLAGS: 00000202 ORIG_RAX: 000000000000002a [ 51.837507] RAX: ffffffffffffffda RBX: 00007ffc9a4a42a8 RCX: 00007f99941965b4 [ 51.837920] RDX: 000000000000001c RSI: 00007ffc9a4a3f10 RDI: 0000000000000008 [ 51.838318] RBP: 00007ffc9a4a3ee0 R08: 0000000000000010 R09: 0000000000000000 [ 51.838721] R10: 00007f999408a730 R11: 0000000000000202 R12: 0000000000000003 [ 51.839126] R13: 0000000000000000 R14: 00007f999433c000 R15: 0000000000ce2d90 [ 51.839527] </TASK> [ 51.839658] [ 51.839759] The buggy address belongs to the object at ffff8881053f0330 [ 51.839759] which belongs to the cache request_sock_TCPv6 of size 344 [ 51.840491] The buggy address is located 92 bytes inside of [ 51.840491] allocated 344-byte region [ffff8881053f0330, ffff8881053f0488) [ 51.841199] [ 51.841298] The buggy address belongs to the physical page: [ 51.841663] page:00000000e92b0bb6 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1053f0 [ 51.842213] head:00000000e92b0bb6 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 51.842741] flags: 0x2fffe0000010200(slab|head|node=0|zone=2|lastcpupid=0x7fff) [ 51.843170] page_type: 0xffffffff() [ 51.843374] raw: 02fffe0000010200 ffff8881016463c0 dead000000000122 0000000000000000 [ 51.843819] raw: 0000000000000000 0000000080140014 00000001ffffffff 0000000000000000 [ 51.844263] page dumped because: kasan: bad access detected [ 51.844578] [ 51.844691] Memory state around the buggy address: [ 51.845125] ffff8881053f0280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 51.845599] ffff8881053f0300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 51.846069] >ffff8881053f0380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 51.846476] ^ [ 51.846684] ffff8881053f0400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 51.847109] ffff8881053f0480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 51.847526] ================================================================== [ 51.847961] Disabling lock debugging due to kernel taint #30/1 btf_skc_cls_ingress/conn:OK #30/2 btf_skc_cls_ingress/syncookie:OK #30 btf_skc_cls_ingress:OK Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED KASAN is pointing to this part of the commit: 0xffffffff8305164d is in tcp_v6_rcv (../include/net/inet6_hashtables.h:122). 117 return NULL; 118 119 if (!prefetched) 120 return sk; 121 122 if (sk->sk_protocol == IPPROTO_TCP) { // bad access 123 if (sk->sk_state != TCP_LISTEN) 124 return sk; 125 } else if (sk->sk_protocol == IPPROTO_UDP) { Let me know if you have trouble reproducing or need any other information.
On Tue, Aug 8, 2023 at 5:23 AM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote: > > Hi Lorenz, Kuniyuki, Martin, > > I am getting a KASAN (inline mode) splat on bpf-next when I run > ./test_progs -t btf_skc_cls_ingress, and I bisected it to this commit: > 9c02bec95954 ("bpf, net: Support SO_REUSEPORT sockets with bpf_sk_assign") Thanks for the report. I forgot about struct request_sock again... I'll have a fix shortly, I hope. Lorenz
diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h index a6722d6ef80f..284b5ce7205d 100644 --- a/include/net/inet6_hashtables.h +++ b/include/net/inet6_hashtables.h @@ -103,6 +103,46 @@ static inline struct sock *__inet6_lookup(struct net *net, daddr, hnum, dif, sdif); } +static inline +struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff, + const struct in6_addr *saddr, const __be16 sport, + const struct in6_addr *daddr, const __be16 dport, + bool *refcounted, inet6_ehashfn_t *ehashfn) +{ + struct sock *sk, *reuse_sk; + bool prefetched; + + sk = skb_steal_sock(skb, refcounted, &prefetched); + if (!sk) + return NULL; + + if (!prefetched) + return sk; + + if (sk->sk_protocol == IPPROTO_TCP) { + if (sk->sk_state != TCP_LISTEN) + return sk; + } else if (sk->sk_protocol == IPPROTO_UDP) { + if (sk->sk_state != TCP_CLOSE) + return sk; + } else { + return sk; + } + + reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, + saddr, sport, daddr, ntohs(dport), + ehashfn); + if (!reuse_sk) + return sk; + + /* We've chosen a new reuseport sock which is never refcounted. This + * implies that sk also isn't refcounted. + */ + WARN_ON_ONCE(*refcounted); + + return reuse_sk; +} + static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, struct sk_buff *skb, int doff, const __be16 sport, @@ -110,14 +150,20 @@ static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, int iif, int sdif, bool *refcounted) { - struct sock *sk = skb_steal_sock(skb, refcounted); - + struct net *net = dev_net(skb_dst(skb)->dev); + const struct ipv6hdr *ip6h = ipv6_hdr(skb); + struct sock *sk; + + sk = inet6_steal_sock(net, skb, doff, &ip6h->saddr, sport, &ip6h->daddr, dport, + refcounted, inet6_ehashfn); + if (IS_ERR(sk)) + return NULL; if (sk) return sk; - return __inet6_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, - doff, &ipv6_hdr(skb)->saddr, sport, - &ipv6_hdr(skb)->daddr, ntohs(dport), + return __inet6_lookup(net, hashinfo, skb, + doff, &ip6h->saddr, sport, + &ip6h->daddr, ntohs(dport), iif, sdif, refcounted); } diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h index c0532cc7587f..1177effabed3 100644 --- a/include/net/inet_hashtables.h +++ b/include/net/inet_hashtables.h @@ -449,6 +449,46 @@ static inline struct sock *inet_lookup(struct net *net, return sk; } +static inline +struct sock *inet_steal_sock(struct net *net, struct sk_buff *skb, int doff, + const __be32 saddr, const __be16 sport, + const __be32 daddr, const __be16 dport, + bool *refcounted, inet_ehashfn_t *ehashfn) +{ + struct sock *sk, *reuse_sk; + bool prefetched; + + sk = skb_steal_sock(skb, refcounted, &prefetched); + if (!sk) + return NULL; + + if (!prefetched) + return sk; + + if (sk->sk_protocol == IPPROTO_TCP) { + if (sk->sk_state != TCP_LISTEN) + return sk; + } else if (sk->sk_protocol == IPPROTO_UDP) { + if (sk->sk_state != TCP_CLOSE) + return sk; + } else { + return sk; + } + + reuse_sk = inet_lookup_reuseport(net, sk, skb, doff, + saddr, sport, daddr, ntohs(dport), + ehashfn); + if (!reuse_sk) + return sk; + + /* We've chosen a new reuseport sock which is never refcounted. This + * implies that sk also isn't refcounted. + */ + WARN_ON_ONCE(*refcounted); + + return reuse_sk; +} + static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, struct sk_buff *skb, int doff, @@ -457,13 +497,18 @@ static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, const int sdif, bool *refcounted) { - struct sock *sk = skb_steal_sock(skb, refcounted); + struct net *net = dev_net(skb_dst(skb)->dev); const struct iphdr *iph = ip_hdr(skb); + struct sock *sk; + sk = inet_steal_sock(net, skb, doff, iph->saddr, sport, iph->daddr, dport, + refcounted, inet_ehashfn); + if (IS_ERR(sk)) + return NULL; if (sk) return sk; - return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, + return __inet_lookup(net, hashinfo, skb, doff, iph->saddr, sport, iph->daddr, dport, inet_iif(skb), sdif, refcounted); diff --git a/include/net/sock.h b/include/net/sock.h index 2eb916d1ff64..320f00e69ae9 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2814,20 +2814,23 @@ sk_is_refcounted(struct sock *sk) * skb_steal_sock - steal a socket from an sk_buff * @skb: sk_buff to steal the socket from * @refcounted: is set to true if the socket is reference-counted + * @prefetched: is set to true if the socket was assigned from bpf */ static inline struct sock * -skb_steal_sock(struct sk_buff *skb, bool *refcounted) +skb_steal_sock(struct sk_buff *skb, bool *refcounted, bool *prefetched) { if (skb->sk) { struct sock *sk = skb->sk; *refcounted = true; - if (skb_sk_is_prefetched(skb)) + *prefetched = skb_sk_is_prefetched(skb); + if (*prefetched) *refcounted = sk_is_refcounted(sk); skb->destructor = NULL; skb->sk = NULL; return sk; } + *prefetched = false; *refcounted = false; return NULL; } diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 739c15906a65..7fc98f4b63e9 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -4198,9 +4198,6 @@ union bpf_attr { * **-EOPNOTSUPP** if the operation is not supported, for example * a call from outside of TC ingress. * - * **-ESOCKTNOSUPPORT** if the socket type is not supported - * (reuseport). - * * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) * Description * Helper is overloaded depending on BPF program type. This diff --git a/net/core/filter.c b/net/core/filter.c index b5b51ef48c5f..7c37f4646c20 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -7351,8 +7351,6 @@ BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) return -EOPNOTSUPP; if (unlikely(dev_net(skb->dev) != sock_net(sk))) return -ENETUNREACH; - if (unlikely(sk_fullsock(sk) && sk->sk_reuseport)) - return -ESOCKTNOSUPPORT; if (sk_unhashed(sk)) return -EOPNOTSUPP; if (sk_is_refcounted(sk) && diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 045eca6ed177..ec1a5f8a2eca 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -2388,7 +2388,11 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, if (udp4_csum_init(skb, uh, proto)) goto csum_error; - sk = skb_steal_sock(skb, &refcounted); + sk = inet_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, + &refcounted, udp_ehashfn); + if (IS_ERR(sk)) + goto no_sk; + if (sk) { struct dst_entry *dst = skb_dst(skb); int ret; @@ -2409,7 +2413,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, udptable); if (sk) return udp_unicast_rcv_skb(sk, skb, uh); - +no_sk: if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) goto drop; nf_reset_ct(skb); diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 109f14b17a09..f6fc75edfa23 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -925,9 +925,9 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; const struct in6_addr *saddr, *daddr; struct net *net = dev_net(skb->dev); + bool refcounted; struct udphdr *uh; struct sock *sk; - bool refcounted; u32 ulen = 0; if (!pskb_may_pull(skb, sizeof(struct udphdr))) @@ -964,7 +964,11 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, goto csum_error; /* Check if the socket is already available, e.g. due to early demux */ - sk = skb_steal_sock(skb, &refcounted); + sk = inet6_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, + &refcounted, udp6_ehashfn); + if (IS_ERR(sk)) + goto no_sk; + if (sk) { struct dst_entry *dst = skb_dst(skb); int ret; @@ -998,7 +1002,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, goto report_csum_error; return udp6_unicast_rcv_skb(sk, skb, uh); } - +no_sk: reason = SKB_DROP_REASON_NO_SOCKET; if (!uh->check) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 739c15906a65..7fc98f4b63e9 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -4198,9 +4198,6 @@ union bpf_attr { * **-EOPNOTSUPP** if the operation is not supported, for example * a call from outside of TC ingress. * - * **-ESOCKTNOSUPPORT** if the socket type is not supported - * (reuseport). - * * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) * Description * Helper is overloaded depending on BPF program type. This
Currently the bpf_sk_assign helper in tc BPF context refuses SO_REUSEPORT sockets. This means we can't use the helper to steer traffic to Envoy, which configures SO_REUSEPORT on its sockets. In turn, we're blocked from removing TPROXY from our setup. The reason that bpf_sk_assign refuses such sockets is that the bpf_sk_lookup helpers don't execute SK_REUSEPORT programs. Instead, one of the reuseport sockets is selected by hash. This could cause dispatch to the "wrong" socket: sk = bpf_sk_lookup_tcp(...) // select SO_REUSEPORT by hash bpf_sk_assign(skb, sk) // SK_REUSEPORT wasn't executed Fixing this isn't as simple as invoking SK_REUSEPORT from the lookup helpers unfortunately. In the tc context, L2 headers are at the start of the skb, while SK_REUSEPORT expects L3 headers instead. Instead, we execute the SK_REUSEPORT program when the assigned socket is pulled out of the skb, further up the stack. This creates some trickiness with regards to refcounting as bpf_sk_assign will put both refcounted and RCU freed sockets in skb->sk. reuseport sockets are RCU freed. We can infer that the sk_assigned socket is RCU freed if the reuseport lookup succeeds, but convincing yourself of this fact isn't straight forward. Therefore we defensively check refcounting on the sk_assign sock even though it's probably not required in practice. Fixes: 8e368dc72e86 ("bpf: Fix use of sk->sk_reuseport from sk_assign") Fixes: cf7fbe660f2d ("bpf: Add socket assign support") Co-developed-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Joe Stringer <joe@cilium.io> Link: https://lore.kernel.org/bpf/CACAyw98+qycmpQzKupquhkxbvWK4OFyDuuLMBNROnfWMZxUWeA@mail.gmail.com/ Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: Lorenz Bauer <lmb@isovalent.com> --- include/net/inet6_hashtables.h | 56 ++++++++++++++++++++++++++++++++++++++---- include/net/inet_hashtables.h | 49 ++++++++++++++++++++++++++++++++++-- include/net/sock.h | 7 ++++-- include/uapi/linux/bpf.h | 3 --- net/core/filter.c | 2 -- net/ipv4/udp.c | 8 ++++-- net/ipv6/udp.c | 10 +++++--- tools/include/uapi/linux/bpf.h | 3 --- 8 files changed, 116 insertions(+), 22 deletions(-)