Set expressions' dump callbacks are not concurrency-safe per-se with
reset bit set. If two CPUs reset the same element at the same time,
values may underrun at least with element-attached counters and quotas.
Prevent this by introducing dedicated callbacks for nfnetlink and the
asynchronous dump handling to serialize access.
Signed-off-by: Phil Sutter <phil@xxxxxx>
---
Changes since v3:
- Perform table and set lookups inside the critical secion
Changes since v2:
- Move the audit_log_nft_set_reset() call into the critical section to
protect the table pointer dereference.
- Drop unused nelems variable from (non-reset) nf_tables_getsetelem().
---
net/netfilter/nf_tables_api.c | 98 +++++++++++++++++++++++++++++------
1 file changed, 81 insertions(+), 17 deletions(-)
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 4e12d0a02e09..1a90ed2e3428 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -5816,10 +5816,6 @@ static int nf_tables_dump_set(struct sk_buff *skb, struct netlink_callback *cb)
nla_nest_end(skb, nest);
nlmsg_end(skb, nlh);
- if (dump_ctx->reset && args.iter.count > args.iter.skip)
- audit_log_nft_set_reset(table, cb->seq,
- args.iter.count - args.iter.skip);
-
rcu_read_unlock();
if (args.iter.err && args.iter.err != -EMSGSIZE)
@@ -5835,6 +5831,26 @@ static int nf_tables_dump_set(struct sk_buff *skb, struct netlink_callback *cb)
return -ENOSPC;
}
+static int nf_tables_dumpreset_set(struct sk_buff *skb,
+ struct netlink_callback *cb)
+{
+ struct nftables_pernet *nft_net = nft_pernet(sock_net(skb->sk));
+ struct nft_set_dump_ctx *dump_ctx = cb->data;
+ int ret, skip = cb->args[0];
+
+ mutex_lock(&nft_net->commit_mutex);
+
+ ret = nf_tables_dump_set(skb, cb);
+
+ if (cb->args[0] > skip)
+ audit_log_nft_set_reset(dump_ctx->ctx.table, cb->seq,
+ cb->args[0] - skip);
+
+ mutex_unlock(&nft_net->commit_mutex);
+
+ return ret;
+}
+
static int nf_tables_dump_set_start(struct netlink_callback *cb)
{
struct nft_set_dump_ctx *dump_ctx = cb->data;
@@ -6078,13 +6094,8 @@ static int nf_tables_getsetelem(struct sk_buff *skb,
{
struct netlink_ext_ack *extack = info->extack;
struct nft_set_dump_ctx dump_ctx;
- int rem, err = 0, nelems = 0;
- struct net *net = info->net;
struct nlattr *attr;
- bool reset = false;
-
- if (NFNL_MSG_TYPE(info->nlh->nlmsg_type) == NFT_MSG_GETSETELEM_RESET)
- reset = true;
+ int rem, err = 0;
if (info->nlh->nlmsg_flags & NLM_F_DUMP) {
struct netlink_dump_control c = {
@@ -6094,7 +6105,7 @@ static int nf_tables_getsetelem(struct sk_buff *skb,
.module = THIS_MODULE,
};
- err = nft_set_dump_ctx_init(&dump_ctx, skb, info, nla, reset);
+ err = nft_set_dump_ctx_init(&dump_ctx, skb, info, nla, false);
if (err)
return err;
@@ -6105,22 +6116,75 @@ static int nf_tables_getsetelem(struct sk_buff *skb,
if (!nla[NFTA_SET_ELEM_LIST_ELEMENTS])
return -EINVAL;
- err = nft_set_dump_ctx_init(&dump_ctx, skb, info, nla, reset);
+ err = nft_set_dump_ctx_init(&dump_ctx, skb, info, nla, false);
if (err)
return err;
nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
- err = nft_get_set_elem(&dump_ctx.ctx, dump_ctx.set, attr, reset);
+ err = nft_get_set_elem(&dump_ctx.ctx, dump_ctx.set, attr, false);
+ if (err < 0) {
+ NL_SET_BAD_ATTR(extack, attr);
+ break;
+ }
+ }
+
+ return err;
+}
+
+static int nf_tables_getsetelem_reset(struct sk_buff *skb,
+ const struct nfnl_info *info,
+ const struct nlattr * const nla[])
+{
+ struct nftables_pernet *nft_net = nft_pernet(info->net);
+ struct netlink_ext_ack *extack = info->extack;
+ struct nft_set_dump_ctx dump_ctx;
+ int rem, err = 0, nelems = 0;
+ struct nlattr *attr;
+
+ if (info->nlh->nlmsg_flags & NLM_F_DUMP) {
+ struct netlink_dump_control c = {
+ .start = nf_tables_dump_set_start,
+ .dump = nf_tables_dumpreset_set,
+ .done = nf_tables_dump_set_done,
+ .module = THIS_MODULE,
+ };
+
+ err = nft_set_dump_ctx_init(&dump_ctx, skb, info, nla, true);
+ if (err)
+ return err;
+
+ c.data = &dump_ctx;
+ return nft_netlink_dump_start_rcu(info->sk, skb, info->nlh, &c);
+ }
+
+ if (!nla[NFTA_SET_ELEM_LIST_ELEMENTS])
+ return -EINVAL;
+
+ if (!try_module_get(THIS_MODULE))
+ return -EINVAL;
+ rcu_read_unlock();
+ mutex_lock(&nft_net->commit_mutex);
+ rcu_read_lock();
+
+ err = nft_set_dump_ctx_init(&dump_ctx, skb, info, nla, true);
+ if (err)
+ goto out_unlock;
+
+ nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
+ err = nft_get_set_elem(&dump_ctx.ctx, dump_ctx.set, attr, true);
if (err < 0) {
NL_SET_BAD_ATTR(extack, attr);
break;
}
nelems++;
}
+ audit_log_nft_set_reset(dump_ctx.ctx.table, nft_net->base_seq, nelems);
- if (reset)
- audit_log_nft_set_reset(dump_ctx.ctx.table, nft_pernet(net)->base_seq,
- nelems);
+out_unlock:
+ rcu_read_unlock();
+ mutex_unlock(&nft_net->commit_mutex);
+ rcu_read_lock();
+ module_put(THIS_MODULE);
return err;
}
@@ -9145,7 +9209,7 @@ static const struct nfnl_callback nf_tables_cb[NFT_MSG_MAX] = {
.policy = nft_set_elem_list_policy,
},
[NFT_MSG_GETSETELEM_RESET] = {
- .call = nf_tables_getsetelem,
+ .call = nf_tables_getsetelem_reset,
.type = NFNL_CB_RCU,
.attr_count = NFTA_SET_ELEM_LIST_MAX,
.policy = nft_set_elem_list_policy,
--
2.41.0
