From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.netfilter.org (mail.netfilter.org [217.70.190.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2CBE733F368 for ; Sat, 26 Sep 2026 08:48:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.190.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790412504; cv=none; b=FoST3efV/DKrO/T6cM/SkdXMCht5PG8tL3BElptqwhC0SriHiprhdRcx0pVfc1nMxzlHhNNZbDQRco2xgNGfg1FS3vDIgEhF61WfFLn6VJIfLhg1QK8eqSX4arFYUpwk3gSQ1EJZciS5HLRXgjrTdaAQ2+EYELaQK4sHAdsCboo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790412504; c=relaxed/simple; bh=qP+vfuYSN0uxxUUacFUqszSGECDnt2lXgSfCiW60ifM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P3pclGDeOGdXmNZ+gZuu/NzoAqj9YMfcGJ0iFvC4fpaHMJlFPY6gWg5zPQfk/aRMiMmOS+gqNlZvUmAJT7hhtCAda5Y/ND3KxYGutt/EBQUrfGzmo50OCQE/Yoad0Dhp7a5RXx+lNxrqTZk93E4ETc98vX3U0PMG+h31nxSa3DI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=netfilter.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b=XSSVievw; arc=none smtp.client-ip=217.70.190.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netfilter.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b="XSSVievw" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1790412490; bh=bfsZ/evKSXGdncdLAo3WOA8KZo4rW0hoGuRtnUcsgKY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XSSVievwNhU2zZPYDp9/9VYIFrH1/7ZvInQZfveq0tPUTtFYSs/xSjlFWmH2crcOk pb2za5laPZv8smChdQtCEc4RiJ/UWbVV+Alnpz4CPk+2yJa+11rEzrAKRYzu8Tqh0+ ZmQOJtDXQiEQM8HUGZMQQWXV9A/BTHO1iXF43ahzLyfHzqu9gCwyWQFXj3lPDiif4p D99DmDTe6qXRwGvuHgLVnmMEG8l1yROuUuc5Hhph+IWh2H1oey8DXnTWm24cRvNh/A lKxbZ9+MbwLSzfkmRjEJDg+72e69IGDB2DvmKMkztNWFtN1QdeMpbpz4l6zfyTN6jD eWHHBiE49NcGQ== Received: from netfilter.org (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with UTF8SMTPSA id 3580D60965; Sat, 26 Sep 2026 10:48:10 +0200 (CEST) Date: Sat, 26 Sep 2026 10:48:07 +0200 From: Pablo Neira Ayuso To: Phil Sutter Cc: netfilter-devel@vger.kernel.org Subject: Re: [nf PATCH v4] netfilter: nfnetlink: Fix for interrupted hook dumps Message-ID: References: <20260909093455.3034863-1-phil@nwl.cc> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Hi Phil, I am preparing a PR with nf fixes and nf-next updates later today. On Fri, Sep 25, 2026 at 04:57:42PM +0200, Phil Sutter wrote: > Bump! > > On Wed, Sep 09, 2026 at 11:34:55AM +0200, Phil Sutter wrote: > > Handling of concurrent hook changes with a dump in progress was > > problematic in nfnl_hook_dump and entirely broken in nfnl_hook_dump_nat. > > Address all issues in a single patch to please the review LLM. > > > > Introduce sequence numbers in struct netns_nf to replace pointer > > value-based modification detection which may fail due to memory buffer > > reuse. This also eliminates the need for most manual cb->seq updates and > > excessive array index value checks. > > > > Since nat hook updates are protected by a different mutex than others, > > they have to bump their own sequence number. nfnl_hook_dump_nat > > therefore open-codes what nl_dump_check_consistent does but bumps > > cb->seq instead of setting NLM_F_DUMP_INTR flag. > > > > Dumps of many nat hooks was entirely broken since the array index was > > not (re)stored. Use cb->args[1] for that and make sure it is reset upon > > completion as the same dump may loop over multiple arrays of nat hooks. > > > > In nfnl_hook_dump, don't signal NLM_F_DUMP_INTR if > > nfnl_hook_entries_head returns error: This is a permanent condition > > which does not change during a dump. It is already caught by > > nfnl_hook_dump_start though, so should not happen anyway. > > > > In general, access ops array pointer values using READ_ONCE since they > > are assigned to using WRITE_ONCE. > > > > Avoid setting NLM_F_DUMP_INTR flag in garbage memory by calling > > nl_dump_check_consistent only for non-empty skbs. If not a single > > netlink message was created, nfnetlink code will take care of setting > > the flag. > > > > Fixes: e2cf17d3774c ("netfilter: add new hook nfnl subsystem") > > Fixes: b010e2a4a9ac ("netfilter: nfnetlink_hook: Dump nat type chains") > > Signed-off-by: Phil Sutter > > --- > > Changes since v3: > > - Bump hook_base_seq after potential array shrinking for consistency > > > > Changes since v2: > > - Bump seq after RCU-pointer assign in __nf_register_net_hook > > - Fix coding style (braces) > > - Rebase onto https://patchwork.ozlabs.org/project/netfilter-devel/patch/20260902232856.1024959-1-pablo@netfilter.org/ > > > > Changes since v1: > > - Reset cursor value and perform EINTR check if NAT priv->entries > > becomes NULL during dump. > > --- > > include/net/netns/netfilter.h | 2 + > > net/netfilter/core.c | 18 ++++++++- > > net/netfilter/nf_nat_core.c | 11 +++++ > > net/netfilter/nfnetlink_hook.c | 74 ++++++++++++++++++++-------------- > > 4 files changed, 73 insertions(+), 32 deletions(-) > > > > diff --git a/include/net/netns/netfilter.h b/include/net/netns/netfilter.h > > index a6a0bf4a247e..7fd78394d1e7 100644 > > --- a/include/net/netns/netfilter.h > > +++ b/include/net/netns/netfilter.h > > @@ -33,5 +33,7 @@ struct netns_nf { > > #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6) > > unsigned int defrag_ipv6_users; > > #endif > > + unsigned int hook_base_seq; > > + unsigned int nat_hook_base_seq; > > }; > > #endif > > diff --git a/net/netfilter/core.c b/net/netfilter/core.c > > index 675a1034b340..940dea2663e9 100644 > > --- a/net/netfilter/core.c > > +++ b/net/netfilter/core.c > > @@ -386,6 +386,15 @@ static void nf_static_key_dec(const struct nf_hook_ops *reg, int pf) > > #endif > > } > > > > +static void bump_hook_base_seq(struct net *net) > > +{ > > + unsigned int base_seq = READ_ONCE(net->nf.hook_base_seq); > > + > > + while (++base_seq == 0) > > + ; > > + smp_store_release(&net->nf.hook_base_seq, base_seq); > > +} > > + > > static int __nf_register_net_hook(struct net *net, int pf, > > const struct nf_hook_ops *reg) > > { > > @@ -430,6 +439,7 @@ static int __nf_register_net_hook(struct net *net, int pf, > > if (!IS_ERR(new_hooks)) { > > hooks_validate(new_hooks); > > rcu_assign_pointer(*pp, new_hooks); > > + bump_hook_base_seq(net); > > } > > > > mutex_unlock(&nf_hook_mutex); > > @@ -483,6 +493,7 @@ static void __nf_unregister_net_hook(struct net *net, int pf, > > { > > struct nf_hook_entries __rcu **pp; > > struct nf_hook_entries *p; > > + bool found; > > > > pp = nf_hook_entry_head(net, pf, reg->hooknum, reg->dev); > > if (!pp) > > @@ -496,7 +507,8 @@ static void __nf_unregister_net_hook(struct net *net, int pf, > > return; > > } > > > > - if (nf_remove_net_hook(p, reg)) { > > + found = nf_remove_net_hook(p, reg); > > + if (found) { > > #ifdef CONFIG_NETFILTER_INGRESS > > if (nf_ingress_hook(reg, pf)) > > net_dec_ingress_queue(); > > @@ -511,6 +523,8 @@ static void __nf_unregister_net_hook(struct net *net, int pf, > > } > > > > p = __nf_hook_entries_try_shrink(p, pp); > > + if (found) > > + bump_hook_base_seq(net); > > mutex_unlock(&nf_hook_mutex); > > if (!p) > > return; > > @@ -784,6 +798,8 @@ static int __net_init netfilter_net_init(struct net *net) > > return -ENOMEM; > > } > > #endif > > + net->nf.hook_base_seq = 1; > > + net->nf.nat_hook_base_seq = 1; > > > > return 0; > > } > > diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c > > index a4858c2b2d65..27d67a677aa4 100644 > > --- a/net/netfilter/nf_nat_core.c > > +++ b/net/netfilter/nf_nat_core.c > > @@ -1160,6 +1160,15 @@ nfnetlink_parse_nat_setup(struct nf_conn *ct, > > } > > #endif > > > > +static void bump_nat_hook_base_seq(struct net *net) > > +{ > > + unsigned int base_seq = READ_ONCE(net->nf.nat_hook_base_seq); > > + > > + while (++base_seq == 0) > > + ; > > + smp_store_release(&net->nf.nat_hook_base_seq, base_seq); > > +} > > + > > static struct nf_ct_helper_expectfn follow_master_nat = { > > .name = "nat-follow-master", > > .expectfn = nf_nat_follow_master, > > @@ -1244,6 +1253,7 @@ int nf_nat_register_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops, > > nat_proto_net->nat_hook_ops = nat_ops; > > > > nat_proto_net->users++; > > + bump_nat_hook_base_seq(net); > > > > mutex_unlock(&nf_nat_proto_mutex); > > > > @@ -1298,6 +1308,7 @@ void nf_nat_unregister_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops, > > goto unlock; > > priv = nat_ops[hooknum].priv; > > nf_hook_entries_delete_raw(&priv->entries, ops); > > + bump_nat_hook_base_seq(net); > > > > if (nat_proto_net->users == 0) { > > nf_unregister_net_hooks(net, nat_ops, ops_count); > > diff --git a/net/netfilter/nfnetlink_hook.c b/net/netfilter/nfnetlink_hook.c > > index 95005e9a6066..b05fd79397c5 100644 > > --- a/net/netfilter/nfnetlink_hook.c > > +++ b/net/netfilter/nfnetlink_hook.c > > @@ -54,7 +54,6 @@ static int nf_netlink_dump_start_rcu(struct sock *nlsk, struct sk_buff *skb, > > > > struct nfnl_dump_hook_data { > > char devname[IFNAMSIZ]; > > - unsigned long headv; > > u8 hook; > > }; > > > > @@ -338,27 +337,47 @@ nfnl_hook_entries_head(u8 pf, unsigned int hook, struct net *net, const char *de > > } > > > > static int nfnl_hook_dump_nat(struct sk_buff *nlskb, > > - const struct nfnl_dump_hook_data *ctx, > > - const struct nf_hook_ops *ops, > > - int family, unsigned int seq) > > + struct netlink_callback *cb, > > + const struct nf_hook_ops *ops, int family) > > { > > struct nf_nat_lookup_hook_priv *priv = ops->priv; > > - struct nf_hook_entries *e = rcu_dereference(priv->entries); > > + struct nfnl_dump_hook_data *ctx = cb->data; > > + struct net *net = sock_net(nlskb->sk); > > struct nf_hook_ops **nat_ops; > > - int i, err; > > + unsigned int i = cb->args[1]; > > + struct nf_hook_entries *e; > > + unsigned int base_seq; > > + int err = 0; > > > > + base_seq = smp_load_acquire(&net->nf.nat_hook_base_seq); > > + > > + e = rcu_dereference(priv->entries); > > if (!e) > > - return 0; > > + goto out; > > > > nat_ops = nf_hook_entries_get_hook_ops(e); > > > > - for (i = 0; i < e->num_hook_entries; i++) { > > - err = nfnl_hook_dump_one(nlskb, ctx, nat_ops[i], > > - ops->priority, family, seq); > > + for (; i < e->num_hook_entries; i++) { > > + err = nfnl_hook_dump_one(nlskb, ctx, > > + READ_ONCE(nat_ops[i]), > > + ops->priority, family, > > + cb->nlh->nlmsg_seq); > > if (err) > > - return err; > > + break; > > + > > } > > - return 0; > > +out: > > + if (!err) > > + i = 0; > > + cb->args[1] = i; > > + > > + if (cb->args[2] && base_seq != cb->args[2]) { > > + cb->seq++; > > + err = -EINTR; > > + } > > + cb->args[2] = base_seq; > > + > > + return err; > > } > > > > static int nfnl_hook_dump(struct sk_buff *nlskb, > > @@ -373,35 +392,31 @@ static int nfnl_hook_dump(struct sk_buff *nlskb, > > unsigned int i = cb->args[0]; > > > > rcu_read_lock(); > > + cb->seq = smp_load_acquire(&net->nf.hook_base_seq); > > > > e = nfnl_hook_entries_head(family, ctx->hook, net, ctx->devname); > > - if (!e) > > + if (!e || IS_ERR(e)) > > goto done; > > > > - if (IS_ERR(e)) { > > - cb->seq++; > > - goto done; > > - } > > - > > - if ((unsigned long)e != ctx->headv || i >= e->num_hook_entries) > > - cb->seq++; > > - > > ops = nf_hook_entries_get_hook_ops(e); > > > > for (; i < e->num_hook_entries; i++) { > > - if (ops[i]->hook_ops_type == NF_HOOK_OP_NAT) > > - err = nfnl_hook_dump_nat(nlskb, ctx, ops[i], family, > > - cb->nlh->nlmsg_seq); > > - else > > - err = nfnl_hook_dump_one(nlskb, ctx, ops[i], > > - ops[i]->priority, family, > > + const struct nf_hook_ops *cur = READ_ONCE(ops[i]); > > + > > + if (cur->hook_ops_type == NF_HOOK_OP_NAT) { > > + err = nfnl_hook_dump_nat(nlskb, cb, cur, family); > > + } else { > > + err = nfnl_hook_dump_one(nlskb, ctx, cur, > > + cur->priority, family, > > cb->nlh->nlmsg_seq); > > + } > > if (err) > > break; > > } > > > > done: > > - nl_dump_check_consistent(cb, nlmsg_hdr(nlskb)); > > + if (nlskb->len > 0) > > + nl_dump_check_consistent(cb, nlmsg_hdr(nlskb)); > > rcu_read_unlock(); > > cb->args[0] = i; > > return nlskb->len; > > @@ -442,10 +457,7 @@ static int nfnl_hook_dump_start(struct netlink_callback *cb) > > return -ENOMEM; > > > > strscpy(ctx->devname, name, sizeof(ctx->devname)); > > - ctx->headv = (unsigned long)head; > > ctx->hook = hooknum; > > - > > - cb->seq = 1; > > cb->data = ctx; > > > > return 0; > > -- > > 2.54.0 > > > > > >