From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- net/ipv4/syncookies.c | 512 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 512 insertions(+) create mode 100644 net/ipv4/syncookies.c (limited to 'net/ipv4/syncookies.c') diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c new file mode 100644 index 000000000..73e129768 --- /dev/null +++ b/net/ipv4/syncookies.c @@ -0,0 +1,512 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Syncookies implementation for the Linux kernel + * + * Copyright (C) 1997 Andi Kleen + * Based on ideas by D.J.Bernstein and Eric Schenk. + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +static siphash_aligned_key_t syncookie_secret[2]; + +#define COOKIEBITS 24 /* Upper bits store count */ +#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1) + +/* TCP Timestamp: 6 lowest bits of timestamp sent in the cookie SYN-ACK + * stores TCP options: + * + * MSB LSB + * | 31 ... 6 | 5 | 4 | 3 2 1 0 | + * | Timestamp | ECN | SACK | WScale | + * + * When we receive a valid cookie-ACK, we look at the echoed tsval (if + * any) to figure out which TCP options we should use for the rebuilt + * connection. + * + * A WScale setting of '0xf' (which is an invalid scaling value) + * means that original syn did not include the TCP window scaling option. + */ +#define TS_OPT_WSCALE_MASK 0xf +#define TS_OPT_SACK BIT(4) +#define TS_OPT_ECN BIT(5) +/* There is no TS_OPT_TIMESTAMP: + * if ACK contains timestamp option, we already know it was + * requested/supported by the syn/synack exchange. + */ +#define TSBITS 6 + +static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport, + u32 count, int c) +{ + net_get_random_once(syncookie_secret, sizeof(syncookie_secret)); + return siphash_4u32((__force u32)saddr, (__force u32)daddr, + (__force u32)sport << 16 | (__force u32)dport, + count, &syncookie_secret[c]); +} + +/* + * when syncookies are in effect and tcp timestamps are enabled we encode + * tcp options in the lower bits of the timestamp value that will be + * sent in the syn-ack. + * Since subsequent timestamps use the normal tcp_time_stamp value, we + * must make sure that the resulting initial timestamp is <= tcp_time_stamp. + */ +u64 cookie_init_timestamp(struct request_sock *req, u64 now) +{ + const struct inet_request_sock *ireq = inet_rsk(req); + u64 ts, ts_now = tcp_ns_to_ts(false, now); + u32 options = 0; + + options = ireq->wscale_ok ? ireq->snd_wscale : TS_OPT_WSCALE_MASK; + if (ireq->sack_ok) + options |= TS_OPT_SACK; + if (ireq->ecn_ok) + options |= TS_OPT_ECN; + + ts = (ts_now >> TSBITS) << TSBITS; + ts |= options; + if (ts > ts_now) + ts -= (1UL << TSBITS); + + if (tcp_rsk(req)->req_usec_ts) + return ts * NSEC_PER_USEC; + return ts * NSEC_PER_MSEC; +} + + +static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport, + __be16 dport, __u32 sseq, __u32 data) +{ + /* + * Compute the secure sequence number. + * The output should be: + * HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24) + * + (HASH(sec2,saddr,sport,daddr,dport,count,sec2) % 2^24). + * Where sseq is their sequence number and count increases every + * minute by 1. + * As an extra hack, we add a small "data" value that encodes the + * MSS into the second hash value. + */ + u32 count = tcp_cookie_time(); + return (cookie_hash(saddr, daddr, sport, dport, 0, 0) + + sseq + (count << COOKIEBITS) + + ((cookie_hash(saddr, daddr, sport, dport, count, 1) + data) + & COOKIEMASK)); +} + +/* + * This retrieves the small "data" value from the syncookie. + * If the syncookie is bad, the data returned will be out of + * range. This must be checked by the caller. + * + * The count value used to generate the cookie must be less than + * MAX_SYNCOOKIE_AGE minutes in the past. + * The return value (__u32)-1 if this test fails. + */ +static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr, + __be16 sport, __be16 dport, __u32 sseq) +{ + u32 diff, count = tcp_cookie_time(); + + /* Strip away the layers from the cookie */ + cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq; + + /* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */ + diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS); + if (diff >= MAX_SYNCOOKIE_AGE) + return (__u32)-1; + + return (cookie - + cookie_hash(saddr, daddr, sport, dport, count - diff, 1)) + & COOKIEMASK; /* Leaving the data behind */ +} + +/* + * MSS Values are chosen based on the 2011 paper + * 'An Analysis of TCP Maximum Segement Sizes' by S. Alcock and R. Nelson. + * Values .. + * .. lower than 536 are rare (< 0.2%) + * .. between 537 and 1299 account for less than < 1.5% of observed values + * .. in the 1300-1349 range account for about 15 to 20% of observed mss values + * .. exceeding 1460 are very rare (< 0.04%) + * + * 1460 is the single most frequently announced mss value (30 to 46% depending + * on monitor location). Table must be sorted. + */ +static __u16 const msstab[] = { + 536, + 1300, + 1440, /* 1440, 1452: PPPoE */ + 1460, +}; + +/* + * Generate a syncookie. mssp points to the mss, which is returned + * rounded down to the value encoded in the cookie. + */ +u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th, + u16 *mssp) +{ + int mssind; + const __u16 mss = *mssp; + + for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--) + if (mss >= msstab[mssind]) + break; + *mssp = msstab[mssind]; + + return secure_tcp_syn_cookie(iph->saddr, iph->daddr, + th->source, th->dest, ntohl(th->seq), + mssind); +} +EXPORT_SYMBOL_GPL(__cookie_v4_init_sequence); + +__u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mssp) +{ + const struct iphdr *iph = ip_hdr(skb); + const struct tcphdr *th = tcp_hdr(skb); + + return __cookie_v4_init_sequence(iph, th, mssp); +} + +/* + * Check if a ack sequence number is a valid syncookie. + * Return the decoded mss if it is, or 0 if not. + */ +int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th) +{ + __u32 cookie = ntohl(th->ack_seq) - 1; + __u32 seq = ntohl(th->seq) - 1; + __u32 mssind; + + mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr, + th->source, th->dest, seq); + + return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0; +} +EXPORT_SYMBOL_GPL(__cookie_v4_check); + +struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb, + struct request_sock *req, + struct dst_entry *dst) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct sock *child; + bool own_req; + + child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst, + NULL, &own_req, NULL); + if (child) { + refcount_set(&req->rsk_refcnt, 1); + sock_rps_save_rxhash(child, skb); + + if (rsk_drop_req(req)) { + reqsk_put(req); + return child; + } + + if (inet_csk_reqsk_queue_add(sk, req, child)) + return child; + + bh_unlock_sock(child); + sock_put(child); + } + __reqsk_free(req); + + return NULL; +} + +/* + * when syncookies are in effect and tcp timestamps are enabled we stored + * additional tcp options in the timestamp. + * This extracts these options from the timestamp echo. + * + * return false if we decode a tcp option that is disabled + * on the host. + */ +bool cookie_timestamp_decode(const struct net *net, + struct tcp_options_received *tcp_opt) +{ + /* echoed timestamp, lowest bits contain options */ + u32 options = tcp_opt->rcv_tsecr; + + if (!tcp_opt->saw_tstamp) { + tcp_clear_options(tcp_opt); + return true; + } + + if (!READ_ONCE(net->ipv4.sysctl_tcp_timestamps)) + return false; + + tcp_opt->sack_ok = (options & TS_OPT_SACK) ? TCP_SACK_SEEN : 0; + + if (tcp_opt->sack_ok && !READ_ONCE(net->ipv4.sysctl_tcp_sack)) + return false; + + if ((options & TS_OPT_WSCALE_MASK) == TS_OPT_WSCALE_MASK) + return true; /* no window scaling */ + + tcp_opt->wscale_ok = 1; + tcp_opt->snd_wscale = options & TS_OPT_WSCALE_MASK; + + return READ_ONCE(net->ipv4.sysctl_tcp_window_scaling) != 0; +} + +static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb, + struct request_sock *req) +{ + struct inet_request_sock *ireq = inet_rsk(req); + struct tcp_request_sock *treq = tcp_rsk(req); + const struct tcphdr *th = tcp_hdr(skb); + + req->num_retrans = 0; + + ireq->ir_num = ntohs(th->dest); + ireq->ir_rmt_port = th->source; + ireq->ir_iif = inet_request_bound_dev_if(sk, skb); + ireq->ir_mark = inet_request_mark(sk, skb); + + if (IS_ENABLED(CONFIG_SMC)) + ireq->smc_ok = 0; + + treq->snt_synack = 0; + treq->snt_tsval_first = 0; + treq->tfo_listener = false; + treq->rcv_isn = ntohl(th->seq) - 1; + treq->snt_isn = ntohl(th->ack_seq) - 1; + /* The request socket was freed after the SYN-ACK; use the cookie + * (snt_isn) as txhash so the full socket and the SYN-ACK make the + * same egress choice (IPv6 ECMP path; IPv4 TX queue). + */ + treq->txhash = treq->snt_isn; + treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield; + +#if IS_ENABLED(CONFIG_MPTCP) + treq->is_mptcp = sk_is_mptcp(sk); + if (treq->is_mptcp) + return mptcp_subflow_init_cookie_req(req, sk, skb); +#endif + + return 0; +} + +#if IS_ENABLED(CONFIG_BPF) +struct request_sock *cookie_bpf_check(struct sock *sk, struct sk_buff *skb) +{ + struct request_sock *req = inet_reqsk(skb->sk); + + skb->sk = NULL; + skb->destructor = NULL; + + if (cookie_tcp_reqsk_init(sk, skb, req)) { + reqsk_free(req); + req = NULL; + } + + return req; +} +#endif + +struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops, + struct sock *sk, struct sk_buff *skb, + struct tcp_options_received *tcp_opt, + int mss, u32 tsoff) +{ + struct inet_request_sock *ireq; + struct tcp_request_sock *treq; + struct request_sock *req; + + if (sk_is_mptcp(sk)) + req = mptcp_subflow_reqsk_alloc(ops, sk, false); + else + req = inet_reqsk_alloc(ops, sk, false); + + if (!req) + return NULL; + + if (cookie_tcp_reqsk_init(sk, skb, req)) { + reqsk_free(req); + return NULL; + } + + ireq = inet_rsk(req); + treq = tcp_rsk(req); + + req->mss = mss; + req->ts_recent = tcp_opt->saw_tstamp ? tcp_opt->rcv_tsval : 0; + + ireq->snd_wscale = tcp_opt->snd_wscale; + ireq->tstamp_ok = tcp_opt->saw_tstamp; + ireq->sack_ok = tcp_opt->sack_ok; + ireq->wscale_ok = tcp_opt->wscale_ok; + ireq->ecn_ok = !!(tcp_opt->rcv_tsecr & TS_OPT_ECN); + + treq->req_usec_ts = false; + treq->ts_off = tsoff; + + return req; +} + +static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk, + struct sk_buff *skb) +{ + struct tcp_options_received tcp_opt; + u32 tsoff = 0; + int mss; + + if (tcp_synq_no_recent_overflow(sk)) + goto out; + + mss = __cookie_v4_check(ip_hdr(skb), tcp_hdr(skb)); + if (!mss) { + __NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED); + goto out; + } + + __NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESRECV); + + /* check for timestamp cookie support */ + memset(&tcp_opt, 0, sizeof(tcp_opt)); + tcp_parse_options(net, skb, &tcp_opt, 0, NULL); + + if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) { + union tcp_seq_and_ts_off st; + + st = secure_tcp_seq_and_ts_off(net, + ip_hdr(skb)->daddr, + ip_hdr(skb)->saddr, + tcp_hdr(skb)->dest, + tcp_hdr(skb)->source); + tsoff = st.ts_off; + tcp_opt.rcv_tsecr -= tsoff; + } + + if (!cookie_timestamp_decode(net, &tcp_opt)) + goto out; + + return cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb, + &tcp_opt, mss, tsoff); +out: + return ERR_PTR(-EINVAL); +} + +/* On input, sk is a listener. + * Output is listener if incoming packet would not create a child + * NULL if memory could not be allocated. + */ +struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) +{ + struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt; + const struct tcphdr *th = tcp_hdr(skb); + struct tcp_sock *tp = tcp_sk(sk); + struct inet_request_sock *ireq; + struct net *net = sock_net(sk); + struct tcp_request_sock *treq; + struct request_sock *req; + struct sock *ret = sk; + struct flowi4 fl4; + struct rtable *rt; + __u8 rcv_wscale; + int full_space; + SKB_DR(reason); + + if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) || + !th->ack || th->rst) + goto out; + + if (cookie_bpf_ok(skb)) { + req = cookie_bpf_check(sk, skb); + } else { + req = cookie_tcp_check(net, sk, skb); + if (IS_ERR(req)) + goto out; + } + if (!req) { + SKB_DR_SET(reason, NO_SOCKET); + goto out_drop; + } + + ireq = inet_rsk(req); + treq = tcp_rsk(req); + + sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr); + sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr); + + /* We throwed the options of the initial SYN away, so we hope + * the ACK carries the same options again (see RFC1122 4.2.3.8) + */ + RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(net, skb)); + + if (security_inet_conn_request(sk, skb, req)) { + SKB_DR_SET(reason, SECURITY_HOOK); + goto out_free; + } + + tcp_ao_syncookie(sk, skb, req, AF_INET); + + /* + * We need to lookup the route here to get at the correct + * window size. We should better make sure that the window size + * hasn't changed since we received the original syn, but I see + * no easy way to do this. + */ + flowi4_init_output(&fl4, ireq->ir_iif, ireq->ir_mark, + ip_sock_rt_tos(sk), ip_sock_rt_scope(sk), + IPPROTO_TCP, inet_sk_flowi_flags(sk), + opt->srr ? opt->faddr : ireq->ir_rmt_addr, + ireq->ir_loc_addr, th->source, th->dest, + sk_uid(sk)); + security_req_classify_flow(req, flowi4_to_flowi_common(&fl4)); + rt = ip_route_output_key(net, &fl4); + if (IS_ERR(rt)) { + SKB_DR_SET(reason, IP_OUTNOROUTES); + goto out_free; + } + + /* Try to redo what tcp_v4_send_synack did. */ + req->rsk_window_clamp = READ_ONCE(tp->window_clamp) ? : + dst_metric(&rt->dst, RTAX_WINDOW); + /* limit the window selection if the user enforce a smaller rx buffer */ + full_space = tcp_full_space(sk); + if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && + (req->rsk_window_clamp > full_space || req->rsk_window_clamp == 0)) + req->rsk_window_clamp = full_space; + + tcp_select_initial_window(sk, full_space, req->mss, + &req->rsk_rcv_wnd, &req->rsk_window_clamp, + ireq->wscale_ok, &rcv_wscale, + dst_metric(&rt->dst, RTAX_INITRWND)); + + /* req->syncookie is set true only if ACK is validated + * by BPF kfunc, then, rcv_wscale is already configured. + */ + if (!req->syncookie) + ireq->rcv_wscale = rcv_wscale; + ireq->ecn_ok &= cookie_ecn_ok(net, &rt->dst); + treq->accecn_ok = ireq->ecn_ok && cookie_accecn_ok(th); + + ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst); + /* ip_queue_xmit() depends on our flow being setup + * Normal sockets get it right from inet_csk_route_child_sock() + */ + if (!ret) { + SKB_DR_SET(reason, NO_SOCKET); + goto out_drop; + } + inet_sk(ret)->cork.fl.u.ip4 = fl4; +out: + return ret; +out_free: + reqsk_free(req); +out_drop: + sk_skb_reason_drop(sk, skb, reason); + return NULL; +} -- cgit v1.3.1