[PATCH nf-next v3 0/7] netfilter: nf_tables: avoid PROVE_RCU_LIST splats

[PATCH nf-next v3 0/7] netfilter: nf_tables: avoid PROVE_RCU_LIST splats

[Florian Westphal]

v3: don't check for type->owner and add comment saying check on
inner_ops is enough.
Use IS_ERR() instead of ptr == NULL in patch 7/7.
No other changes.

Mathieu reported a lockdep splat on rule deletion with
CONFIG_RCU_LIST=y.

Unfortunately there are many more errors, and not all are false positives.

First patches pass lockdep_commit_lock_is_held() to the rcu list traversal
macro so that those splats are avoided.

The last two patches are real code change as opposed to
'pass the transaction mutex to relax rcu check':

Those two lists are not protected by transaction mutex so could be altered
in parallel in case of module load/removal.

Florian Westphal (7):
  netfilter: nf_tables: avoid false-positive lockdep splat on rule
    deletion
  netfilter: nf_tables: avoid false-positive lockdep splats with sets
  netfilter: nf_tables: avoid false-positive lockdep splats with
    flowtables
  netfilter: nf_tables: avoid false-positive lockdep splats in set
    walker
  netfilter: nf_tables: avoid false-positive lockdep splats with
    basechain hook
  netfilter: nf_tables: must hold rcu read lock while iterating
    expression type list
  netfilter: nf_tables: must hold rcu read lock while iterating object
    type list

 include/net/netfilter/nf_tables.h |   3 +-
 net/netfilter/nf_tables_api.c     | 110 ++++++++++++++++++------------
 net/netfilter/nft_flow_offload.c  |   4 +-
 net/netfilter/nft_set_bitmap.c    |  10 +--
 net/netfilter/nft_set_hash.c      |   3 +-
 5 files changed, 79 insertions(+), 51 deletions(-)

-- 
2.45.2

[PATCH nf-next v3 1/7] netfilter: nf_tables: avoid false-positive lockdep splat on rule deletion

[Florian Westphal]

On rule delete we get:
 WARNING: suspicious RCU usage
 net/netfilter/nf_tables_api.c:3420 RCU-list traversed in non-reader section!!
 1 lock held by iptables/134:
   #0: ffff888008c4fcc8 (&nft_net->commit_mutex){+.+.}-{3:3}, at: nf_tables_valid_genid (include/linux/jiffies.h:101) nf_tables

Code is fine, no other CPU can change the list because we're holding
transaction mutex.

Pass the needed lockdep annotation to the iterator and fix
two comments for functions that are no longer restricted to rcu-only
context.

This is enough to resolve rule delete, but there are several other
missing annotations, added in followup-patches.

Fixes: 28875945ba98 ("rcu: Add support for consolidated-RCU reader checking")
Reported-by: Matthieu Baerts <matttbe@kernel.org>
Tested-by: Matthieu Baerts <matttbe@kernel.org>
Closes: https://lore.kernel.org/netfilter-devel/da27f17f-3145-47af-ad0f-7fd2a823623e@kernel.org/
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 30331688301e..80c285ac7e07 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3411,13 +3411,15 @@ void nft_expr_destroy(const struct nft_ctx *ctx, struct nft_expr *expr)
  * Rules
  */
 
-static struct nft_rule *__nft_rule_lookup(const struct nft_chain *chain,
+static struct nft_rule *__nft_rule_lookup(const struct net *net,
+					  const struct nft_chain *chain,
 					  u64 handle)
 {
 	struct nft_rule *rule;
 
 	// FIXME: this sucks
-	list_for_each_entry_rcu(rule, &chain->rules, list) {
+	list_for_each_entry_rcu(rule, &chain->rules, list,
+				lockdep_commit_lock_is_held(net)) {
 		if (handle == rule->handle)
 			return rule;
 	}
@@ -3425,13 +3427,14 @@ static struct nft_rule *__nft_rule_lookup(const struct nft_chain *chain,
 	return ERR_PTR(-ENOENT);
 }
 
-static struct nft_rule *nft_rule_lookup(const struct nft_chain *chain,
+static struct nft_rule *nft_rule_lookup(const struct net *net,
+					const struct nft_chain *chain,
 					const struct nlattr *nla)
 {
 	if (nla == NULL)
 		return ERR_PTR(-EINVAL);
 
-	return __nft_rule_lookup(chain, be64_to_cpu(nla_get_be64(nla)));
+	return __nft_rule_lookup(net, chain, be64_to_cpu(nla_get_be64(nla)));
 }
 
 static const struct nla_policy nft_rule_policy[NFTA_RULE_MAX + 1] = {
@@ -3732,7 +3735,7 @@ static int nf_tables_dump_rules_done(struct netlink_callback *cb)
 	return 0;
 }
 
-/* called with rcu_read_lock held */
+/* Caller must hold rcu read lock or transaction mutex */
 static struct sk_buff *
 nf_tables_getrule_single(u32 portid, const struct nfnl_info *info,
 			 const struct nlattr * const nla[], bool reset)
@@ -3759,7 +3762,7 @@ nf_tables_getrule_single(u32 portid, const struct nfnl_info *info,
 		return ERR_CAST(chain);
 	}
 
-	rule = nft_rule_lookup(chain, nla[NFTA_RULE_HANDLE]);
+	rule = nft_rule_lookup(net, chain, nla[NFTA_RULE_HANDLE]);
 	if (IS_ERR(rule)) {
 		NL_SET_BAD_ATTR(extack, nla[NFTA_RULE_HANDLE]);
 		return ERR_CAST(rule);
@@ -4057,7 +4060,7 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
 
 	if (nla[NFTA_RULE_HANDLE]) {
 		handle = be64_to_cpu(nla_get_be64(nla[NFTA_RULE_HANDLE]));
-		rule = __nft_rule_lookup(chain, handle);
+		rule = __nft_rule_lookup(net, chain, handle);
 		if (IS_ERR(rule)) {
 			NL_SET_BAD_ATTR(extack, nla[NFTA_RULE_HANDLE]);
 			return PTR_ERR(rule);
@@ -4079,7 +4082,7 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
 
 		if (nla[NFTA_RULE_POSITION]) {
 			pos_handle = be64_to_cpu(nla_get_be64(nla[NFTA_RULE_POSITION]));
-			old_rule = __nft_rule_lookup(chain, pos_handle);
+			old_rule = __nft_rule_lookup(net, chain, pos_handle);
 			if (IS_ERR(old_rule)) {
 				NL_SET_BAD_ATTR(extack, nla[NFTA_RULE_POSITION]);
 				return PTR_ERR(old_rule);
@@ -4296,7 +4299,7 @@ static int nf_tables_delrule(struct sk_buff *skb, const struct nfnl_info *info,
 
 	if (chain) {
 		if (nla[NFTA_RULE_HANDLE]) {
-			rule = nft_rule_lookup(chain, nla[NFTA_RULE_HANDLE]);
+			rule = nft_rule_lookup(info->net, chain, nla[NFTA_RULE_HANDLE]);
 			if (IS_ERR(rule)) {
 				if (PTR_ERR(rule) == -ENOENT &&
 				    NFNL_MSG_TYPE(info->nlh->nlmsg_type) == NFT_MSG_DESTROYRULE)
@@ -8101,7 +8104,7 @@ static int nf_tables_dump_obj_done(struct netlink_callback *cb)
 	return 0;
 }
 
-/* called with rcu_read_lock held */
+/* Caller must hold rcu read lock or transaction mutex */
 static struct sk_buff *
 nf_tables_getobj_single(u32 portid, const struct nfnl_info *info,
 			const struct nlattr * const nla[], bool reset)
-- 
2.45.2

[PATCH nf-next v3 2/7] netfilter: nf_tables: avoid false-positive lockdep splats with sets

[Florian Westphal]

Same as previous patch.  All set handling functions here can be called
with transaction mutex held (but not the rcu read lock).

The transaction mutex prevents concurrent add/delete, so this is fine.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 80c285ac7e07..a51731d76401 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3986,7 +3986,8 @@ int nft_set_catchall_validate(const struct nft_ctx *ctx, struct nft_set *set)
 	struct nft_set_ext *ext;
 	int ret = 0;
 
-	list_for_each_entry_rcu(catchall, &set->catchall_list, list) {
+	list_for_each_entry_rcu(catchall, &set->catchall_list, list,
+				lockdep_commit_lock_is_held(ctx->net)) {
 		ext = nft_set_elem_ext(set, catchall->elem);
 		if (!nft_set_elem_active(ext, dummy_iter.genmask))
 			continue;
@@ -4459,7 +4460,8 @@ static const struct nla_policy nft_set_desc_policy[NFTA_SET_DESC_MAX + 1] = {
 	[NFTA_SET_DESC_CONCAT]		= NLA_POLICY_NESTED_ARRAY(nft_concat_policy),
 };
 
-static struct nft_set *nft_set_lookup(const struct nft_table *table,
+static struct nft_set *nft_set_lookup(const struct net *net,
+				      const struct nft_table *table,
 				      const struct nlattr *nla, u8 genmask)
 {
 	struct nft_set *set;
@@ -4467,7 +4469,8 @@ static struct nft_set *nft_set_lookup(const struct nft_table *table,
 	if (nla == NULL)
 		return ERR_PTR(-EINVAL);
 
-	list_for_each_entry_rcu(set, &table->sets, list) {
+	list_for_each_entry_rcu(set, &table->sets, list,
+				lockdep_commit_lock_is_held(net)) {
 		if (!nla_strcmp(nla, set->name) &&
 		    nft_active_genmask(set, genmask))
 			return set;
@@ -4517,7 +4520,7 @@ struct nft_set *nft_set_lookup_global(const struct net *net,
 {
 	struct nft_set *set;
 
-	set = nft_set_lookup(table, nla_set_name, genmask);
+	set = nft_set_lookup(net, table, nla_set_name, genmask);
 	if (IS_ERR(set)) {
 		if (!nla_set_id)
 			return set;
@@ -4893,7 +4896,7 @@ static int nf_tables_getset(struct sk_buff *skb, const struct nfnl_info *info,
 	if (!nla[NFTA_SET_TABLE])
 		return -EINVAL;
 
-	set = nft_set_lookup(table, nla[NFTA_SET_NAME], genmask);
+	set = nft_set_lookup(net, table, nla[NFTA_SET_NAME], genmask);
 	if (IS_ERR(set)) {
 		NL_SET_BAD_ATTR(extack, nla[NFTA_SET_NAME]);
 		return PTR_ERR(set);
@@ -5229,7 +5232,7 @@ static int nf_tables_newset(struct sk_buff *skb, const struct nfnl_info *info,
 
 	nft_ctx_init(&ctx, net, skb, info->nlh, family, table, NULL, nla);
 
-	set = nft_set_lookup(table, nla[NFTA_SET_NAME], genmask);
+	set = nft_set_lookup(net, table, nla[NFTA_SET_NAME], genmask);
 	if (IS_ERR(set)) {
 		if (PTR_ERR(set) != -ENOENT) {
 			NL_SET_BAD_ATTR(extack, nla[NFTA_SET_NAME]);
@@ -5431,7 +5434,7 @@ static int nf_tables_delset(struct sk_buff *skb, const struct nfnl_info *info,
 		set = nft_set_lookup_byhandle(table, attr, genmask);
 	} else {
 		attr = nla[NFTA_SET_NAME];
-		set = nft_set_lookup(table, attr, genmask);
+		set = nft_set_lookup(net, table, attr, genmask);
 	}
 
 	if (IS_ERR(set)) {
@@ -5495,7 +5498,8 @@ static int nft_set_catchall_bind_check(const struct nft_ctx *ctx,
 	struct nft_set_ext *ext;
 	int ret = 0;
 
-	list_for_each_entry_rcu(catchall, &set->catchall_list, list) {
+	list_for_each_entry_rcu(catchall, &set->catchall_list, list,
+				lockdep_commit_lock_is_held(ctx->net)) {
 		ext = nft_set_elem_ext(set, catchall->elem);
 		if (!nft_set_elem_active(ext, genmask))
 			continue;
@@ -6261,7 +6265,7 @@ static int nft_set_dump_ctx_init(struct nft_set_dump_ctx *dump_ctx,
 		return PTR_ERR(table);
 	}
 
-	set = nft_set_lookup(table, nla[NFTA_SET_ELEM_LIST_SET], genmask);
+	set = nft_set_lookup(net, table, nla[NFTA_SET_ELEM_LIST_SET], genmask);
 	if (IS_ERR(set)) {
 		NL_SET_BAD_ATTR(extack, nla[NFTA_SET_ELEM_LIST_SET]);
 		return PTR_ERR(set);
@@ -7493,7 +7497,8 @@ static int nft_set_catchall_flush(const struct nft_ctx *ctx,
 	struct nft_set_ext *ext;
 	int ret = 0;
 
-	list_for_each_entry_rcu(catchall, &set->catchall_list, list) {
+	list_for_each_entry_rcu(catchall, &set->catchall_list, list,
+				lockdep_commit_lock_is_held(ctx->net)) {
 		ext = nft_set_elem_ext(set, catchall->elem);
 		if (!nft_set_elem_active(ext, genmask))
 			continue;
@@ -7543,7 +7548,7 @@ static int nf_tables_delsetelem(struct sk_buff *skb,
 		return PTR_ERR(table);
 	}
 
-	set = nft_set_lookup(table, nla[NFTA_SET_ELEM_LIST_SET], genmask);
+	set = nft_set_lookup(net, table, nla[NFTA_SET_ELEM_LIST_SET], genmask);
 	if (IS_ERR(set)) {
 		NL_SET_BAD_ATTR(extack, nla[NFTA_SET_ELEM_LIST_SET]);
 		return PTR_ERR(set);
-- 
2.45.2

[PATCH nf-next v3 3/7] netfilter: nf_tables: avoid false-positive lockdep splats with flowtables

[Florian Westphal]

The transaction mutex prevents concurrent add/delete, its ok to iterate
those lists outside of rcu read side critical sections.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 include/net/netfilter/nf_tables.h |  3 ++-
 net/netfilter/nf_tables_api.c     | 15 +++++++++------
 net/netfilter/nft_flow_offload.c  |  4 ++--
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 91ae20cb7648..c1513bd14568 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -1463,7 +1463,8 @@ struct nft_flowtable {
 	struct nf_flowtable		data;
 };
 
-struct nft_flowtable *nft_flowtable_lookup(const struct nft_table *table,
+struct nft_flowtable *nft_flowtable_lookup(const struct net *net,
+					   const struct nft_table *table,
 					   const struct nlattr *nla,
 					   u8 genmask);
 
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index a51731d76401..9e367e134691 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -8378,12 +8378,14 @@ static const struct nla_policy nft_flowtable_policy[NFTA_FLOWTABLE_MAX + 1] = {
 	[NFTA_FLOWTABLE_FLAGS]		= { .type = NLA_U32 },
 };
 
-struct nft_flowtable *nft_flowtable_lookup(const struct nft_table *table,
+struct nft_flowtable *nft_flowtable_lookup(const struct net *net,
+					   const struct nft_table *table,
 					   const struct nlattr *nla, u8 genmask)
 {
 	struct nft_flowtable *flowtable;
 
-	list_for_each_entry_rcu(flowtable, &table->flowtables, list) {
+	list_for_each_entry_rcu(flowtable, &table->flowtables, list,
+				lockdep_commit_lock_is_held(net)) {
 		if (!nla_strcmp(nla, flowtable->name) &&
 		    nft_active_genmask(flowtable, genmask))
 			return flowtable;
@@ -8739,7 +8741,7 @@ static int nf_tables_newflowtable(struct sk_buff *skb,
 		return PTR_ERR(table);
 	}
 
-	flowtable = nft_flowtable_lookup(table, nla[NFTA_FLOWTABLE_NAME],
+	flowtable = nft_flowtable_lookup(net, table, nla[NFTA_FLOWTABLE_NAME],
 					 genmask);
 	if (IS_ERR(flowtable)) {
 		err = PTR_ERR(flowtable);
@@ -8933,7 +8935,7 @@ static int nf_tables_delflowtable(struct sk_buff *skb,
 		flowtable = nft_flowtable_lookup_byhandle(table, attr, genmask);
 	} else {
 		attr = nla[NFTA_FLOWTABLE_NAME];
-		flowtable = nft_flowtable_lookup(table, attr, genmask);
+		flowtable = nft_flowtable_lookup(net, table, attr, genmask);
 	}
 
 	if (IS_ERR(flowtable)) {
@@ -9003,7 +9005,8 @@ static int nf_tables_fill_flowtable_info(struct sk_buff *skb, struct net *net,
 	if (!hook_list)
 		hook_list = &flowtable->hook_list;
 
-	list_for_each_entry_rcu(hook, hook_list, list) {
+	list_for_each_entry_rcu(hook, hook_list, list,
+				lockdep_commit_lock_is_held(net)) {
 		if (nla_put_string(skb, NFTA_DEVICE_NAME, hook->ops.dev->name))
 			goto nla_put_failure;
 	}
@@ -9145,7 +9148,7 @@ static int nf_tables_getflowtable(struct sk_buff *skb,
 		return PTR_ERR(table);
 	}
 
-	flowtable = nft_flowtable_lookup(table, nla[NFTA_FLOWTABLE_NAME],
+	flowtable = nft_flowtable_lookup(net, table, nla[NFTA_FLOWTABLE_NAME],
 					 genmask);
 	if (IS_ERR(flowtable)) {
 		NL_SET_BAD_ATTR(extack, nla[NFTA_FLOWTABLE_NAME]);
diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c
index 2f732fae5a83..65199c23c75c 100644
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c
@@ -409,8 +409,8 @@ static int nft_flow_offload_init(const struct nft_ctx *ctx,
 	if (!tb[NFTA_FLOW_TABLE_NAME])
 		return -EINVAL;
 
-	flowtable = nft_flowtable_lookup(ctx->table, tb[NFTA_FLOW_TABLE_NAME],
-					 genmask);
+	flowtable = nft_flowtable_lookup(ctx->net, ctx->table,
+					 tb[NFTA_FLOW_TABLE_NAME], genmask);
 	if (IS_ERR(flowtable))
 		return PTR_ERR(flowtable);
 
-- 
2.45.2

[PATCH nf-next v3 4/7] netfilter: nf_tables: avoid false-positive lockdep splats in set walker

[Florian Westphal]

Its not possible to add or delete elements from hash and bitmap sets,
as long as caller is holding the transaction mutex, so its ok to iterate
the list outside of rcu read side critical section.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nft_set_bitmap.c | 10 ++++++----
 net/netfilter/nft_set_hash.c   |  3 ++-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/nft_set_bitmap.c b/net/netfilter/nft_set_bitmap.c
index 1caa04619dc6..12390d2e994f 100644
--- a/net/netfilter/nft_set_bitmap.c
+++ b/net/netfilter/nft_set_bitmap.c
@@ -88,13 +88,15 @@ bool nft_bitmap_lookup(const struct net *net, const struct nft_set *set,
 }
 
 static struct nft_bitmap_elem *
-nft_bitmap_elem_find(const struct nft_set *set, struct nft_bitmap_elem *this,
+nft_bitmap_elem_find(const struct net *net,
+		     const struct nft_set *set, struct nft_bitmap_elem *this,
 		     u8 genmask)
 {
 	const struct nft_bitmap *priv = nft_set_priv(set);
 	struct nft_bitmap_elem *be;
 
-	list_for_each_entry_rcu(be, &priv->list, head) {
+	list_for_each_entry_rcu(be, &priv->list, head,
+				lockdep_is_held(&nft_pernet(net)->commit_mutex)) {
 		if (memcmp(nft_set_ext_key(&be->ext),
 			   nft_set_ext_key(&this->ext), set->klen) ||
 		    !nft_set_elem_active(&be->ext, genmask))
@@ -132,7 +134,7 @@ static int nft_bitmap_insert(const struct net *net, const struct nft_set *set,
 	u8 genmask = nft_genmask_next(net);
 	u32 idx, off;
 
-	be = nft_bitmap_elem_find(set, new, genmask);
+	be = nft_bitmap_elem_find(net, set, new, genmask);
 	if (be) {
 		*elem_priv = &be->priv;
 		return -EEXIST;
@@ -201,7 +203,7 @@ nft_bitmap_deactivate(const struct net *net, const struct nft_set *set,
 
 	nft_bitmap_location(set, elem->key.val.data, &idx, &off);
 
-	be = nft_bitmap_elem_find(set, this, genmask);
+	be = nft_bitmap_elem_find(net, set, this, genmask);
 	if (!be)
 		return NULL;
 
diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c
index daa56dda737a..65bd291318f2 100644
--- a/net/netfilter/nft_set_hash.c
+++ b/net/netfilter/nft_set_hash.c
@@ -647,7 +647,8 @@ static void nft_hash_walk(const struct nft_ctx *ctx, struct nft_set *set,
 	int i;
 
 	for (i = 0; i < priv->buckets; i++) {
-		hlist_for_each_entry_rcu(he, &priv->table[i], node) {
+		hlist_for_each_entry_rcu(he, &priv->table[i], node,
+					 lockdep_is_held(&nft_pernet(ctx->net)->commit_mutex)) {
 			if (iter->count < iter->skip)
 				goto cont;
 
-- 
2.45.2

[PATCH nf-next v3 5/7] netfilter: nf_tables: avoid false-positive lockdep splats with basechain hook

[Florian Westphal]

Like previous patches: iteration is ok if the list cannot be altered in
parallel.

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 9e367e134691..3b5154f2dd79 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1824,7 +1824,8 @@ static int nft_dump_stats(struct sk_buff *skb, struct nft_stats __percpu *stats)
 	return -ENOSPC;
 }
 
-static int nft_dump_basechain_hook(struct sk_buff *skb, int family,
+static int nft_dump_basechain_hook(struct sk_buff *skb,
+				   const struct net *net, int family,
 				   const struct nft_base_chain *basechain,
 				   const struct list_head *hook_list)
 {
@@ -1849,7 +1850,8 @@ static int nft_dump_basechain_hook(struct sk_buff *skb, int family,
 		if (!hook_list)
 			hook_list = &basechain->hook_list;
 
-		list_for_each_entry_rcu(hook, hook_list, list) {
+		list_for_each_entry_rcu(hook, hook_list, list,
+					lockdep_commit_lock_is_held(net)) {
 			if (!first)
 				first = hook;
 
@@ -1900,7 +1902,7 @@ static int nf_tables_fill_chain_info(struct sk_buff *skb, struct net *net,
 		const struct nft_base_chain *basechain = nft_base_chain(chain);
 		struct nft_stats __percpu *stats;
 
-		if (nft_dump_basechain_hook(skb, family, basechain, hook_list))
+		if (nft_dump_basechain_hook(skb, net, family, basechain, hook_list))
 			goto nla_put_failure;
 
 		if (nla_put_be32(skb, NFTA_CHAIN_POLICY,
-- 
2.45.2

[PATCH nf-next v3 6/7] netfilter: nf_tables: must hold rcu read lock while iterating expression type list

[Florian Westphal]

nft shell tests trigger:
 WARNING: suspicious RCU usage
 net/netfilter/nf_tables_api.c:3125 RCU-list traversed in non-reader section!!
 1 lock held by nft/2068:
  #0: ffff888106c6f8c8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nf_tables_valid_genid+0x3c/0xf0

But the transaction mutex doesn't protect this list, the nfnl subsystem
mutex would, but we can't acquire it here without risk of ABBA
deadlocks.

Acquire the rcu read lock to avoid this issue.

v3: add a comment that explains the ->inner_ops check implies
expression is builtin and lack of a module owner reference is ok.

Fixes: 3a07327d10a0 ("netfilter: nft_inner: support for inner tunnel header matching")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 3b5154f2dd79..de8e48a5c62d 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3296,25 +3296,37 @@ int nft_expr_inner_parse(const struct nft_ctx *ctx, const struct nlattr *nla,
 	if (!tb[NFTA_EXPR_DATA] || !tb[NFTA_EXPR_NAME])
 		return -EINVAL;
 
+	rcu_read_lock();
+
 	type = __nft_expr_type_get(ctx->family, tb[NFTA_EXPR_NAME]);
-	if (!type)
-		return -ENOENT;
+	if (!type) {
+		err = -ENOENT;
+		goto out_unlock;
+	}
 
-	if (!type->inner_ops)
-		return -EOPNOTSUPP;
+	if (!type->inner_ops) {
+		err = -EOPNOTSUPP;
+		goto out_unlock;
+	}
 
 	err = nla_parse_nested_deprecated(info->tb, type->maxattr,
 					  tb[NFTA_EXPR_DATA],
 					  type->policy, NULL);
 	if (err < 0)
-		goto err_nla_parse;
+		goto out_unlock;
 
 	info->attr = nla;
 	info->ops = type->inner_ops;
 
+	/* No module reference will be taken on type->owner.
+	 * Presence of type->inner_ops implies that the expression
+	 * is builtin, so it cannot go away.
+	 */
+	rcu_read_unlock();
 	return 0;
 
-err_nla_parse:
+out_unlock:
+	rcu_read_unlock();
 	return err;
 }
 
-- 
2.45.2

[PATCH nf-next v3 7/7] netfilter: nf_tables: must hold rcu read lock while iterating object type list

[Florian Westphal]

Update of stateful object triggers:
WARNING: suspicious RCU usage
net/netfilter/nf_tables_api.c:7759 RCU-list traversed in non-reader section!!

other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
1 lock held by nft/3060:
 #0: ffff88810f0578c8 (&nft_net->commit_mutex){+.+.}-{4:4}, [..]

... but this list is not protected by the transaction mutex but the
nfnl nftables subsystem mutex.

Switch to nft_obj_type_get which will acquire rcu read lock,
bump refcount, and returns the result.

v3: Dan Carpenter points out nft_obj_type_get returns error pointer, not
NULL, on error.

Fixes: dad3bdeef45f ("netfilter: nf_tables: fix memory leak during stateful obj update").
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index de8e48a5c62d..b7a817e483aa 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -7809,9 +7809,7 @@ static int nf_tables_updobj(const struct nft_ctx *ctx,
 	struct nft_trans *trans;
 	int err = -ENOMEM;
 
-	if (!try_module_get(type->owner))
-		return -ENOENT;
-
+	/* caller must have obtained type->owner reference. */
 	trans = nft_trans_alloc(ctx, NFT_MSG_NEWOBJ,
 				sizeof(struct nft_trans_obj));
 	if (!trans)
@@ -7879,15 +7877,16 @@ static int nf_tables_newobj(struct sk_buff *skb, const struct nfnl_info *info,
 		if (info->nlh->nlmsg_flags & NLM_F_REPLACE)
 			return -EOPNOTSUPP;
 
-		type = __nft_obj_type_get(objtype, family);
-		if (WARN_ON_ONCE(!type))
-			return -ENOENT;
-
 		if (!obj->ops->update)
 			return 0;
 
+		type = nft_obj_type_get(net, objtype, family);
+		if (WARN_ON_ONCE(IS_ERR(type)))
+			return PTR_ERR(type);
+
 		nft_ctx_init(&ctx, net, skb, info->nlh, family, table, NULL, nla);
 
+		/* type->owner reference is put when transaction object is released. */
 		return nf_tables_updobj(&ctx, type, nla[NFTA_OBJ_DATA], obj);
 	}
 
-- 
2.45.2

Re: [PATCH nf-next v3 0/7] netfilter: nf_tables: avoid PROVE_RCU_LIST splats

[Pablo Neira Ayuso]

On Mon, Nov 04, 2024 at 10:41:12AM +0100, Florian Westphal wrote:
> v3: don't check for type->owner and add comment saying check on
> inner_ops is enough.
> Use IS_ERR() instead of ptr == NULL in patch 7/7.
> No other changes.
> 
> Mathieu reported a lockdep splat on rule deletion with
> CONFIG_RCU_LIST=y.
> 
> Unfortunately there are many more errors, and not all are false positives.
> 
> First patches pass lockdep_commit_lock_is_held() to the rcu list traversal
> macro so that those splats are avoided.
> 
> The last two patches are real code change as opposed to
> 'pass the transaction mutex to relax rcu check':
> 
> Those two lists are not protected by transaction mutex so could be altered
> in parallel in case of module load/removal.

I have placed this series in nf-next testing branch.

Thanks Florian.