This is a note to let you know that I've just added the patch titled

netfilter: nfnl_cthelper: fix a race when walk the nf_ct_helper_hash table

to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: netfilter-nfnl_cthelper-fix-a-race-when-walk-the-nf_ct_helper_hash-table.patch and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Dec 21 10:55:04 CET 2017

From: Liping Zhang zlpnobody@gmail.com Date: Sat, 25 Mar 2017 12:09:15 +0800 Subject: netfilter: nfnl_cthelper: fix a race when walk the nf_ct_helper_hash table

From: Liping Zhang zlpnobody@gmail.com

[ Upstream commit 83d90219a5df8d950855ce73229a97b63605c317 ]

The nf_ct_helper_hash table is protected by nf_ct_helper_mutex, while nfct_helper operation is protected by nfnl_lock(NFNL_SUBSYS_CTHELPER). So it's possible that one CPU is walking the nf_ct_helper_hash for cthelper add/get/del, another cpu is doing nf_conntrack_helpers_unregister at the same time. This is dangrous, and may cause use after free error.

Note, delete operation will flush all cthelpers added via nfnetlink, so using rcu to do protect is not easy.

Now introduce a dummy list to record all the cthelpers added via nfnetlink, then we can walk the dummy list instead of walking the nf_ct_helper_hash. Also, keep nfnl_cthelper_dump_table unchanged, it may be invoked without nfnl_lock(NFNL_SUBSYS_CTHELPER) held.

Signed-off-by: Liping Zhang zlpnobody@gmail.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/netfilter/nfnetlink_cthelper.c | 185 +++++++++++++++++-------------------- 1 file changed, 85 insertions(+), 100 deletions(-)

--- a/net/netfilter/nfnetlink_cthelper.c +++ b/net/netfilter/nfnetlink_cthelper.c @@ -32,6 +32,13 @@ MODULE_LICENSE("GPL"); MODULE_AUTHOR("Pablo Neira Ayuso pablo@netfilter.org"); MODULE_DESCRIPTION("nfnl_cthelper: User-space connection tracking helpers");

+struct nfnl_cthelper { + struct list_head list; + struct nf_conntrack_helper helper; +}; + +static LIST_HEAD(nfnl_cthelper_list); + static int nfnl_userspace_cthelper(struct sk_buff *skb, unsigned int protoff, struct nf_conn *ct, enum ip_conntrack_info ctinfo) @@ -205,14 +212,16 @@ nfnl_cthelper_create(const struct nlattr struct nf_conntrack_tuple *tuple) { struct nf_conntrack_helper *helper; + struct nfnl_cthelper *nfcth; int ret;

if (!tb[NFCTH_TUPLE] || !tb[NFCTH_POLICY] || !tb[NFCTH_PRIV_DATA_LEN]) return -EINVAL;

- helper = kzalloc(sizeof(struct nf_conntrack_helper), GFP_KERNEL); - if (helper == NULL) + nfcth = kzalloc(sizeof(*nfcth), GFP_KERNEL); + if (nfcth == NULL) return -ENOMEM; + helper = &nfcth->helper;

ret = nfnl_cthelper_parse_expect_policy(helper, tb[NFCTH_POLICY]); if (ret < 0) @@ -249,11 +258,12 @@ nfnl_cthelper_create(const struct nlattr if (ret < 0) goto err2;

+ list_add_tail(&nfcth->list, &nfnl_cthelper_list); return 0; err2: kfree(helper->expect_policy); err1: - kfree(helper); + kfree(nfcth); return ret; }

@@ -379,7 +389,8 @@ nfnl_cthelper_new(struct sock *nfnl, str const char *helper_name; struct nf_conntrack_helper *cur, *helper = NULL; struct nf_conntrack_tuple tuple; - int ret = 0, i; + struct nfnl_cthelper *nlcth; + int ret = 0;

if (!tb[NFCTH_NAME] || !tb[NFCTH_TUPLE]) return -EINVAL; @@ -390,31 +401,22 @@ nfnl_cthelper_new(struct sock *nfnl, str if (ret < 0) return ret;

- rcu_read_lock(); - for (i = 0; i < nf_ct_helper_hsize && !helper; i++) { - hlist_for_each_entry_rcu(cur, &nf_ct_helper_hash[i], hnode) { + list_for_each_entry(nlcth, &nfnl_cthelper_list, list) { + cur = &nlcth->helper;

- /* skip non-userspace conntrack helpers. */ - if (!(cur->flags & NF_CT_HELPER_F_USERSPACE)) - continue; + if (strncmp(cur->name, helper_name, NF_CT_HELPER_NAME_LEN)) + continue;

- if (strncmp(cur->name, helper_name, - NF_CT_HELPER_NAME_LEN) != 0) - continue; + if ((tuple.src.l3num != cur->tuple.src.l3num || + tuple.dst.protonum != cur->tuple.dst.protonum)) + continue;

- if ((tuple.src.l3num != cur->tuple.src.l3num || - tuple.dst.protonum != cur->tuple.dst.protonum)) - continue; + if (nlh->nlmsg_flags & NLM_F_EXCL) + return -EEXIST;

- if (nlh->nlmsg_flags & NLM_F_EXCL) { - ret = -EEXIST; - goto err; - } - helper = cur; - break; - } + helper = cur; + break; } - rcu_read_unlock();

if (helper == NULL) ret = nfnl_cthelper_create(tb, &tuple); @@ -422,9 +424,6 @@ nfnl_cthelper_new(struct sock *nfnl, str ret = nfnl_cthelper_update(tb, helper);

return ret; -err: - rcu_read_unlock(); - return ret; }

static int @@ -588,11 +587,12 @@ static int nfnl_cthelper_get(struct sock *nfnl, struct sk_buff *skb, const struct nlmsghdr *nlh, const struct nlattr * const tb[]) { - int ret = -ENOENT, i; + int ret = -ENOENT; struct nf_conntrack_helper *cur; struct sk_buff *skb2; char *helper_name = NULL; struct nf_conntrack_tuple tuple; + struct nfnl_cthelper *nlcth; bool tuple_set = false;

if (nlh->nlmsg_flags & NLM_F_DUMP) { @@ -613,45 +613,39 @@ nfnl_cthelper_get(struct sock *nfnl, str tuple_set = true; }

- for (i = 0; i < nf_ct_helper_hsize; i++) { - hlist_for_each_entry_rcu(cur, &nf_ct_helper_hash[i], hnode) { - - /* skip non-userspace conntrack helpers. */ - if (!(cur->flags & NF_CT_HELPER_F_USERSPACE)) - continue; - - if (helper_name && strncmp(cur->name, helper_name, - NF_CT_HELPER_NAME_LEN) != 0) { - continue; - } - if (tuple_set && - (tuple.src.l3num != cur->tuple.src.l3num || - tuple.dst.protonum != cur->tuple.dst.protonum)) - continue; - - skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL); - if (skb2 == NULL) { - ret = -ENOMEM; - break; - } + list_for_each_entry(nlcth, &nfnl_cthelper_list, list) { + cur = &nlcth->helper; + if (helper_name && + strncmp(cur->name, helper_name, NF_CT_HELPER_NAME_LEN)) + continue; + + if (tuple_set && + (tuple.src.l3num != cur->tuple.src.l3num || + tuple.dst.protonum != cur->tuple.dst.protonum)) + continue; + + skb2 = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL); + if (skb2 == NULL) { + ret = -ENOMEM; + break; + }

- ret = nfnl_cthelper_fill_info(skb2, NETLINK_CB(skb).portid, - nlh->nlmsg_seq, - NFNL_MSG_TYPE(nlh->nlmsg_type), - NFNL_MSG_CTHELPER_NEW, cur); - if (ret <= 0) { - kfree_skb(skb2); - break; - } + ret = nfnl_cthelper_fill_info(skb2, NETLINK_CB(skb).portid, + nlh->nlmsg_seq, + NFNL_MSG_TYPE(nlh->nlmsg_type), + NFNL_MSG_CTHELPER_NEW, cur); + if (ret <= 0) { + kfree_skb(skb2); + break; + }

- ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid, - MSG_DONTWAIT); - if (ret > 0) - ret = 0; + ret = netlink_unicast(nfnl, skb2, NETLINK_CB(skb).portid, + MSG_DONTWAIT); + if (ret > 0) + ret = 0;

- /* this avoids a loop in nfnetlink. */ - return ret == -EAGAIN ? -ENOBUFS : ret; - } + /* this avoids a loop in nfnetlink. */ + return ret == -EAGAIN ? -ENOBUFS : ret; } return ret; } @@ -662,10 +656,10 @@ nfnl_cthelper_del(struct sock *nfnl, str { char *helper_name = NULL; struct nf_conntrack_helper *cur; - struct hlist_node *tmp; struct nf_conntrack_tuple tuple; bool tuple_set = false, found = false; - int i, j = 0, ret; + struct nfnl_cthelper *nlcth, *n; + int j = 0, ret;

if (tb[NFCTH_NAME]) helper_name = nla_data(tb[NFCTH_NAME]); @@ -678,30 +672,27 @@ nfnl_cthelper_del(struct sock *nfnl, str tuple_set = true; }

- for (i = 0; i < nf_ct_helper_hsize; i++) { - hlist_for_each_entry_safe(cur, tmp, &nf_ct_helper_hash[i], - hnode) { - /* skip non-userspace conntrack helpers. */ - if (!(cur->flags & NF_CT_HELPER_F_USERSPACE)) - continue; - - j++; - - if (helper_name && strncmp(cur->name, helper_name, - NF_CT_HELPER_NAME_LEN) != 0) { - continue; - } - if (tuple_set && - (tuple.src.l3num != cur->tuple.src.l3num || - tuple.dst.protonum != cur->tuple.dst.protonum)) - continue; + list_for_each_entry_safe(nlcth, n, &nfnl_cthelper_list, list) { + cur = &nlcth->helper; + j++; + + if (helper_name && + strncmp(cur->name, helper_name, NF_CT_HELPER_NAME_LEN)) + continue; + + if (tuple_set && + (tuple.src.l3num != cur->tuple.src.l3num || + tuple.dst.protonum != cur->tuple.dst.protonum)) + continue; + + found = true; + nf_conntrack_helper_unregister(cur); + kfree(cur->expect_policy);

- found = true; - nf_conntrack_helper_unregister(cur); - kfree(cur->expect_policy); - kfree(cur); - } + list_del(&nlcth->list); + kfree(nlcth); } + /* Make sure we return success if we flush and there is no helpers */ return (found || j == 0) ? 0 : -ENOENT; } @@ -750,22 +741,16 @@ err_out: static void __exit nfnl_cthelper_exit(void) { struct nf_conntrack_helper *cur; - struct hlist_node *tmp; - int i; + struct nfnl_cthelper *nlcth, *n;

nfnetlink_subsys_unregister(&nfnl_cthelper_subsys);

- for (i=0; i<nf_ct_helper_hsize; i++) { - hlist_for_each_entry_safe(cur, tmp, &nf_ct_helper_hash[i], - hnode) { - /* skip non-userspace conntrack helpers. */ - if (!(cur->flags & NF_CT_HELPER_F_USERSPACE)) - continue; + list_for_each_entry_safe(nlcth, n, &nfnl_cthelper_list, list) { + cur = &nlcth->helper;

- nf_conntrack_helper_unregister(cur); - kfree(cur->expect_policy); - kfree(cur); - } + nf_conntrack_helper_unregister(cur); + kfree(cur->expect_policy); + kfree(nlcth); } }

Patches currently in stable-queue which might be from zlpnobody@gmail.com are

queue-3.18/netfilter-nfnl_cthelper-fix-runtime-expectation-policy-updates.patch queue-3.18/netfilter-nfnl_cthelper-fix-a-race-when-walk-the-nf_ct_helper_hash-table.patch