TCP and SCTP conntrack paths can emit invalid-packet logs while ct->lock is still held. When invalid logging is routed to nfnetlink_log and conntrack export is enabled, the log path can re-enter conntrack netlink glue and dump the same conntrack again. Protocol attribute dumping may take ct->lock, so logging while holding that lock can deadlock. Defer the TCP invalid logs by storing only the minimal log context while ct->lock is held and emitting the log after unlocking. Also make the TCP timeout-lowering invalid path return whether a log is needed, then emit that log after unlocking. Do the same for the SCTP invalid state-transition log that can be reached while ct->lock is held. Add a lockdep assertion to nf_ct_l4proto_log_invalid() so future callers that log invalid conntracks while holding ct->lock are caught outside TCP and SCTP as well. Fixes: 628d694344a0 ("netfilter: conntrack: reduce timeout when receiving out-of-window fin or rst") Fixes: d9a6f0d0df18 ("netfilter: conntrack: prepare tcp_in_window for ternary return value") Fixes: f71cb8f45d09 ("netfilter: conntrack: sctp: use nf log infrastructure for invalid packets") Cc: stable@vger.kernel.org Reported-by: Vega Assisted-by: Codex:gpt-5.4 Signed-off-by: Zihan Xi Reviewed-by: Florian Westphal --- changes in v3: - Squash the previous two TCP patches into one patch as requested. - Include the SCTP invalid state-transition log in the same logical fix. - Move the lockdep assertion and recursion comment into nf_ct_l4proto_log_invalid(). - Adjust the TCP local declaration order per review. - Use the broader nf_conntrack subject suggested by Pablo. - Correct the Fixes: set to the first held-lock invalid-log call sites. - Keep Florian Westphal's Reviewed-by. - v2 Link: https://lore.kernel.org/all/cover.1785348197.git.zihanx@nebusec.ai/ changes in v2: - Split the TCP timeout-lowering and tcp_in_window() handling for review. - Switch the reproducer documentation to the packetdrill wrapper flow. - Keep the decoded crash log and real reproduction artifacts in the cover letter. - v1 Link: https://lore.kernel.org/all/cover.1785307980.git.zihanx@nebusec.ai/ --- net/netfilter/nf_conntrack_proto.c | 6 ++ net/netfilter/nf_conntrack_proto_sctp.c | 12 ++- net/netfilter/nf_conntrack_proto_tcp.c | 132 ++++++++++++++++-------- 3 files changed, 102 insertions(+), 48 deletions(-) diff --git a/net/netfilter/nf_conntrack_proto.c b/net/netfilter/nf_conntrack_proto.c index ad96896516b6..9439596f34e6 100644 --- a/net/netfilter/nf_conntrack_proto.c +++ b/net/netfilter/nf_conntrack_proto.c @@ -83,6 +83,12 @@ void nf_ct_l4proto_log_invalid(const struct sk_buff *skb, if (likely(net->ct.sysctl_log_invalid == 0)) return; + /* nfnetlink_log may re-enter conntrack attribute dumping and try to + * take ct->lock again via helpers such as tcp_to_nlattr(), so invalid + * conntrack logs must only be emitted after dropping ct->lock. + */ + lockdep_assert_not_held(&ct->lock); + va_start(args, fmt); vaf.fmt = fmt; vaf.va = &args; diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c index 7e10fa65cbdd..dd90f1df9d55 100644 --- a/net/netfilter/nf_conntrack_proto_sctp.c +++ b/net/netfilter/nf_conntrack_proto_sctp.c @@ -339,7 +339,9 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct, u_int32_t offset, count; unsigned int *timeouts; unsigned long map[256 / sizeof(unsigned long)] = { 0 }; + bool log_invalid = false; bool ignore = false; + u8 invalid_type = 0; if (sctp_error(skb, dataoff, state)) return -NF_ACCEPT; @@ -451,10 +453,8 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct, /* Invalid */ if (new_state == SCTP_CONNTRACK_MAX) { - nf_ct_l4proto_log_invalid(skb, ct, state, - "Invalid, old_state %d, dir %d, type %d", - old_state, dir, sch->type); - + log_invalid = true; + invalid_type = sch->type; goto out_unlock; } @@ -529,6 +529,10 @@ int nf_conntrack_sctp_packet(struct nf_conn *ct, out_unlock: spin_unlock_bh(&ct->lock); + if (log_invalid) + nf_ct_l4proto_log_invalid(skb, ct, state, + "Invalid, old_state %d, dir %d, type %d", + old_state, dir, invalid_type); out: return -NF_ACCEPT; } diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c index ceeed3d7fe52..93272aafd289 100644 --- a/net/netfilter/nf_conntrack_proto_tcp.c +++ b/net/netfilter/nf_conntrack_proto_tcp.c @@ -480,37 +480,81 @@ static void tcp_init_sender(struct ip_ct_tcp_state *sender, } } -__printf(6, 7) -static enum nf_ct_tcp_action nf_tcp_log_invalid(const struct sk_buff *skb, - const struct nf_conn *ct, - const struct nf_hook_state *state, - const struct ip_ct_tcp_state *sender, - enum nf_ct_tcp_action ret, - const char *fmt, ...) +enum nf_tcp_invalid_log_type { + NF_TCP_LOG_NONE, + NF_TCP_LOG_OVERSHOT, + NF_TCP_LOG_SEQ_OVER, + NF_TCP_LOG_ACK_OVER, + NF_TCP_LOG_SEQ_UNDER, + NF_TCP_LOG_ACK_UNDER, +}; + +struct nf_tcp_invalid_log { + enum nf_tcp_invalid_log_type type; + u32 value; +}; + +static enum nf_ct_tcp_action +nf_tcp_store_invalid(const struct nf_conn *ct, + const struct ip_ct_tcp_state *sender, + struct nf_tcp_invalid_log *log, + enum nf_ct_tcp_action ret, + enum nf_tcp_invalid_log_type type, + u32 value) { const struct nf_tcp_net *tn = nf_tcp_pernet(nf_ct_net(ct)); - struct va_format vaf; - va_list args; bool be_liberal; be_liberal = sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL || tn->tcp_be_liberal; if (be_liberal) return NFCT_TCP_ACCEPT; - va_start(args, fmt); - vaf.fmt = fmt; - vaf.va = &args; - nf_ct_l4proto_log_invalid(skb, ct, state, "%pV", &vaf); - va_end(args); - + log->type = type; + log->value = value; return ret; } +static void nf_tcp_log_invalid(const struct sk_buff *skb, + const struct nf_conn *ct, + const struct nf_hook_state *state, + const struct nf_tcp_invalid_log *log) +{ + switch (log->type) { + case NF_TCP_LOG_OVERSHOT: + nf_ct_l4proto_log_invalid(skb, ct, state, + "%u bytes more than expected", + log->value); + break; + case NF_TCP_LOG_SEQ_OVER: + nf_ct_l4proto_log_invalid(skb, ct, state, + "SEQ is over upper bound %u (over the window of the receiver)", + log->value); + break; + case NF_TCP_LOG_ACK_OVER: + nf_ct_l4proto_log_invalid(skb, ct, state, + "ACK is over upper bound %u (ACKed data not seen yet)", + log->value); + break; + case NF_TCP_LOG_SEQ_UNDER: + nf_ct_l4proto_log_invalid(skb, ct, state, + "SEQ is under lower bound %u (already ACKed data retransmitted)", + log->value); + break; + case NF_TCP_LOG_ACK_UNDER: + nf_ct_l4proto_log_invalid(skb, ct, state, + "ignored ACK under lower bound %u (possible overly delayed)", + log->value); + break; + case NF_TCP_LOG_NONE: + break; + } +} + static enum nf_ct_tcp_action tcp_in_window(struct nf_conn *ct, enum ip_conntrack_dir dir, unsigned int index, const struct sk_buff *skb, unsigned int dataoff, const struct tcphdr *tcph, - const struct nf_hook_state *hook_state) + struct nf_tcp_invalid_log *log) { struct ip_ct_tcp *state = &ct->proto.tcp; struct ip_ct_tcp_state *sender = &state->seen[dir]; @@ -640,31 +684,29 @@ tcp_in_window(struct nf_conn *ct, enum ip_conntrack_dir dir, sender->td_end = end; sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED; - return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, - "%u bytes more than expected", overshot); + return nf_tcp_store_invalid(ct, sender, log, NFCT_TCP_IGNORE, + NF_TCP_LOG_OVERSHOT, overshot); } - return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID, - "SEQ is over upper bound %u (over the window of the receiver)", - sender->td_maxend + 1); + return nf_tcp_store_invalid(ct, sender, log, NFCT_TCP_INVALID, + NF_TCP_LOG_SEQ_OVER, sender->td_maxend + 1); } if (!before(sack, receiver->td_end + 1)) - return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID, - "ACK is over upper bound %u (ACKed data not seen yet)", - receiver->td_end + 1); + return nf_tcp_store_invalid(ct, sender, log, NFCT_TCP_INVALID, + NF_TCP_LOG_ACK_OVER, receiver->td_end + 1); /* Is the ending sequence in the receive window (if available)? */ in_recv_win = !receiver->td_maxwin || after(end, sender->td_end - receiver->td_maxwin - 1); if (!in_recv_win) - return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, - "SEQ is under lower bound %u (already ACKed data retransmitted)", - sender->td_end - receiver->td_maxwin - 1); + return nf_tcp_store_invalid(ct, sender, log, NFCT_TCP_IGNORE, + NF_TCP_LOG_SEQ_UNDER, + sender->td_end - receiver->td_maxwin - 1); if (!after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) - return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, - "ignored ACK under lower bound %u (possible overly delayed)", - receiver->td_end - MAXACKWINDOW(sender) - 1); + return nf_tcp_store_invalid(ct, sender, log, NFCT_TCP_IGNORE, + NF_TCP_LOG_ACK_UNDER, + receiver->td_end - MAXACKWINDOW(sender) - 1); /* Take into account window scaling (RFC 1323). */ if (!tcph->syn) @@ -719,11 +761,8 @@ tcp_in_window(struct nf_conn *ct, enum ip_conntrack_dir dir, return NFCT_TCP_ACCEPT; } -static void __cold nf_tcp_handle_invalid(struct nf_conn *ct, - enum ip_conntrack_dir dir, - int index, - const struct sk_buff *skb, - const struct nf_hook_state *hook_state) +static bool __cold +nf_tcp_handle_invalid(struct nf_conn *ct, enum ip_conntrack_dir dir, int index) { const unsigned int *timeouts; const struct nf_tcp_net *tn; @@ -732,7 +771,7 @@ static void __cold nf_tcp_handle_invalid(struct nf_conn *ct, if (!test_bit(IPS_ASSURED_BIT, &ct->status) || test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) - return; + return false; /* We don't want to have connections hanging around in ESTABLISHED * state for long time 'just because' conntrack deemed a FIN/RST @@ -747,7 +786,7 @@ static void __cold nf_tcp_handle_invalid(struct nf_conn *ct, case TCP_FIN_SET: break; default: - return; + return false; } if (ct->proto.tcp.last_dir != dir && @@ -755,7 +794,7 @@ static void __cold nf_tcp_handle_invalid(struct nf_conn *ct, ct->proto.tcp.last_index == TCP_RST_SET)) { expires = nf_ct_expires(ct); if (expires < 120 * HZ) - return; + return false; tn = nf_tcp_pernet(nf_ct_net(ct)); timeouts = nf_ct_timeout_lookup(ct); @@ -764,16 +803,15 @@ static void __cold nf_tcp_handle_invalid(struct nf_conn *ct, timeout = READ_ONCE(timeouts[TCP_CONNTRACK_UNACK]); if (expires > timeout) { - nf_ct_l4proto_log_invalid(skb, ct, hook_state, - "packet (index %d, dir %d) response for index %d lower timeout to %u", - index, dir, ct->proto.tcp.last_index, timeout); - WRITE_ONCE(ct->timeout, timeout + nfct_time_stamp); + return true; } } else { ct->proto.tcp.last_index = index; ct->proto.tcp.last_dir = dir; } + + return false; } /* table of valid flag combinations - PUSH, ECE and CWR are always valid */ @@ -970,7 +1008,9 @@ int nf_conntrack_tcp_packet(struct nf_conn *ct, struct nf_tcp_net *tn = nf_tcp_pernet(net); enum tcp_conntrack new_state, old_state; unsigned int index, *timeouts; + bool lowered_timeout = false; enum nf_ct_tcp_action res; + struct nf_tcp_invalid_log log = {}; enum ip_conntrack_dir dir; const struct tcphdr *th; struct tcphdr _tcph; @@ -1252,14 +1292,18 @@ int nf_conntrack_tcp_packet(struct nf_conn *ct, } res = tcp_in_window(ct, dir, index, - skb, dataoff, th, state); + skb, dataoff, th, &log); switch (res) { case NFCT_TCP_IGNORE: spin_unlock_bh(&ct->lock); + nf_tcp_log_invalid(skb, ct, state, &log); return NF_ACCEPT; case NFCT_TCP_INVALID: - nf_tcp_handle_invalid(ct, dir, index, skb, state); + lowered_timeout = nf_tcp_handle_invalid(ct, dir, index); spin_unlock_bh(&ct->lock); + nf_tcp_log_invalid(skb, ct, state, &log); + if (lowered_timeout) + nf_ct_l4proto_log_invalid(skb, ct, state, "lowered timeout to UNACK"); return -NF_ACCEPT; case NFCT_TCP_ACCEPT: break; -- 2.43.0