From 3f7c72bc4227b169ba2c924a7987324e24bbc4b2 Mon Sep 17 00:00:00 2001 From: Vlad Buslov Date: Thu, 5 Jul 2018 17:24:26 +0300 Subject: [PATCH] net: sched: always take reference to action Without rtnl lock protection it is no longer safe to use pointer to tc action without holding reference to it. (it can be destroyed concurrently) Remove unsafe action idr lookup function. Instead of it, implement safe tcf idr check function that atomically looks up action in idr and increments its reference and bind counters. Implement both action search and check using new safe function Reference taken by idr check is temporal and should not be accounted by userspace clients (both logically and to preserver current API behavior). Subtract temporal reference when dumping action to userspace using existing tca_get_fill function arguments. Reviewed-by: Marcelo Ricardo Leitner Signed-off-by: Vlad Buslov Signed-off-by: Jiri Pirko Signed-off-by: David S. Miller --- net/sched/act_api.c | 46 ++++++++++++++++++++------------------------- 1 file changed, 20 insertions(+), 26 deletions(-) diff --git a/net/sched/act_api.c b/net/sched/act_api.c index 256b0c93916c..aa304d36fee0 100644 --- a/net/sched/act_api.c +++ b/net/sched/act_api.c @@ -284,44 +284,38 @@ int tcf_generic_walker(struct tc_action_net *tn, struct sk_buff *skb, } EXPORT_SYMBOL(tcf_generic_walker); -static struct tc_action *tcf_idr_lookup(u32 index, struct tcf_idrinfo *idrinfo) +static bool __tcf_idr_check(struct tc_action_net *tn, u32 index, + struct tc_action **a, int bind) { - struct tc_action *p = NULL; + struct tcf_idrinfo *idrinfo = tn->idrinfo; + struct tc_action *p; spin_lock(&idrinfo->lock); p = idr_find(&idrinfo->action_idr, index); + if (p) { + refcount_inc(&p->tcfa_refcnt); + if (bind) + atomic_inc(&p->tcfa_bindcnt); + } spin_unlock(&idrinfo->lock); - return p; + if (p) { + *a = p; + return true; + } + return false; } int tcf_idr_search(struct tc_action_net *tn, struct tc_action **a, u32 index) { - struct tcf_idrinfo *idrinfo = tn->idrinfo; - struct tc_action *p = tcf_idr_lookup(index, idrinfo); - - if (p) { - *a = p; - return 1; - } - return 0; + return __tcf_idr_check(tn, index, a, 0); } EXPORT_SYMBOL(tcf_idr_search); bool tcf_idr_check(struct tc_action_net *tn, u32 index, struct tc_action **a, int bind) { - struct tcf_idrinfo *idrinfo = tn->idrinfo; - struct tc_action *p = tcf_idr_lookup(index, idrinfo); - - if (index && p) { - if (bind) - atomic_inc(&p->tcfa_bindcnt); - refcount_inc(&p->tcfa_refcnt); - *a = p; - return true; - } - return false; + return __tcf_idr_check(tn, index, a, bind); } EXPORT_SYMBOL(tcf_idr_check); @@ -932,7 +926,7 @@ tcf_get_notify(struct net *net, u32 portid, struct nlmsghdr *n, if (!skb) return -ENOBUFS; if (tca_get_fill(skb, actions, portid, n->nlmsg_seq, 0, event, - 0, 0) <= 0) { + 0, 1) <= 0) { NL_SET_ERR_MSG(extack, "Failed to fill netlink attributes while adding TC action"); kfree_skb(skb); return -EINVAL; @@ -1072,7 +1066,7 @@ tcf_del_notify(struct net *net, struct nlmsghdr *n, struct list_head *actions, return -ENOBUFS; if (tca_get_fill(skb, actions, portid, n->nlmsg_seq, 0, RTM_DELACTION, - 0, 1) <= 0) { + 0, 2) <= 0) { NL_SET_ERR_MSG(extack, "Failed to fill netlink TC action attributes"); kfree_skb(skb); return -EINVAL; @@ -1131,14 +1125,14 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct nlmsghdr *n, if (event == RTM_GETACTION) ret = tcf_get_notify(net, portid, n, &actions, event, extack); else { /* delete */ + cleanup_a(&actions, 1); /* lookup took reference */ ret = tcf_del_notify(net, n, &actions, portid, attr_size, extack); if (ret) goto err; return ret; } err: - if (event != RTM_GETACTION) - tcf_action_destroy(&actions, 0); + tcf_action_destroy(&actions, 0); return ret; }