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netfilter: nf_tables: Add locking for NFT_MSG_GETSETELEM_RESET requests 

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@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Phil Sutter 2023-11-09 16:01:16 +01:00 committed by Pablo Neira Ayuso
parent f649be6d9c
commit 3d483faa66
1 changed files with 81 additions and 17 deletions
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98
net/netfilter/nf_tables_api.c
View File

@ -5817,10 +5817,6 @@ 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)
@ -5836,6 +5832,26 @@ nla_put_failure:
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;
@ -6079,13 +6095,8 @@ 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 = {
@ -6095,7 +6106,7 @@ 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;
@ -6106,22 +6117,75 @@ 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;
}
@ -9095,7 +9159,7 @@ 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,