From 22e6625babfc1fe349032cd46237085b91aae076 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Tue, 22 Sep 2020 20:56:24 -0700 Subject: net_sched: commit action insertions together commit 0fedc63fadf0404a729e73a35349481c8009c02f upstream. syzbot is able to trigger a failure case inside the loop in tcf_action_init(), and when this happens we clean up with tcf_action_destroy(). But, as these actions are already inserted into the global IDR, other parallel process could free them before tcf_action_destroy(), then we will trigger a use-after-free. Fix this by deferring the insertions even later, after the loop, and committing all the insertions in a separate loop, so we will never fail in the middle of the insertions any more. One side effect is that the window between alloction and final insertion becomes larger, now it is more likely that the loop in tcf_del_walker() sees the placeholder -EBUSY pointer. So we have to check for error pointer in tcf_del_walker(). Reported-and-tested-by: syzbot+2287853d392e4b42374a@syzkaller.appspotmail.com Fixes: 0190c1d452a9 ("net: sched: atomically check-allocate action") Cc: Vlad Buslov Cc: Jamal Hadi Salim Cc: Jiri Pirko Signed-off-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/sched/act_api.c | 32 +++++++++++++++++++++++--------- 1 file changed, 23 insertions(+), 9 deletions(-) (limited to 'net') diff --git a/net/sched/act_api.c b/net/sched/act_api.c index fea74060d2c3..4a5ef2adb2e5 100644 --- a/net/sched/act_api.c +++ b/net/sched/act_api.c @@ -303,6 +303,8 @@ static int tcf_del_walker(struct tcf_idrinfo *idrinfo, struct sk_buff *skb, mutex_lock(&idrinfo->lock); idr_for_each_entry_ul(idr, p, tmp, id) { + if (IS_ERR(p)) + continue; ret = tcf_idr_release_unsafe(p); if (ret == ACT_P_DELETED) { module_put(ops->owner); @@ -828,14 +830,24 @@ static const struct nla_policy tcf_action_policy[TCA_ACT_MAX + 1] = { [TCA_ACT_OPTIONS] = { .type = NLA_NESTED }, }; -static void tcf_idr_insert(struct tc_action *a) +static void tcf_idr_insert_many(struct tc_action *actions[]) { - struct tcf_idrinfo *idrinfo = a->idrinfo; + int i; - mutex_lock(&idrinfo->lock); - /* Replace ERR_PTR(-EBUSY) allocated by tcf_idr_check_alloc */ - WARN_ON(!IS_ERR(idr_replace(&idrinfo->action_idr, a, a->tcfa_index))); - mutex_unlock(&idrinfo->lock); + for (i = 0; i < TCA_ACT_MAX_PRIO; i++) { + struct tc_action *a = actions[i]; + struct tcf_idrinfo *idrinfo; + + if (!a) + continue; + idrinfo = a->idrinfo; + mutex_lock(&idrinfo->lock); + /* Replace ERR_PTR(-EBUSY) allocated by tcf_idr_check_alloc if + * it is just created, otherwise this is just a nop. + */ + idr_replace(&idrinfo->action_idr, a, a->tcfa_index); + mutex_unlock(&idrinfo->lock); + } } struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp, @@ -927,9 +939,6 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp, return ERR_PTR(-EINVAL); } - if (err == ACT_P_CREATED) - tcf_idr_insert(a); - if (!name && tb[TCA_ACT_COOKIE]) tcf_set_action_cookie(&a->act_cookie, cookie); @@ -983,6 +992,11 @@ int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla, actions[i - 1] = act; } + /* We have to commit them all together, because if any error happened in + * between, we could not handle the failure gracefully. + */ + tcf_idr_insert_many(actions); + *attr_size = tcf_action_full_attrs_size(sz); return i - 1; -- cgit v1.2.3