net: sched: cls_u32 changes to knode must appear atomic to readers
Changes to the cls_u32 classifier must appear atomic to the readers. Before this patch if a change is requested for both the exts and ifindex, first the ifindex is updated then the exts with tcf_exts_change(). This opens a small window where a reader can have a exts chain with an incorrect ifindex. This violates the the RCU semantics. Here we resolve this by always passing u32_set_parms() a copy of the tc_u_knode to work on and then inserting it into the hash table after the updates have been successfully applied. Tested with the following short script: #tc filter add dev p3p2 parent 8001:0 protocol ip prio 99 handle 1: \ u32 divisor 256 #tc filter add dev p3p2 parent 8001:0 protocol ip prio 99 \ u32 link 1: hashkey mask ffffff00 at 12 \ match ip src 192.168.8.0/2 #tc filter add dev p3p2 parent 8001:0 protocol ip prio 102 \ handle 1::10 u32 classid 1:2 ht 1: \ match ip src 192.168.8.0/8 match ip tos 0x0a 1e #tc filter change dev p3p2 parent 8001:0 protocol ip prio 102 \ handle 1::10 u32 classid 1:2 ht 1: \ match ip src 1.1.0.0/8 match ip tos 0x0b 1e CC: Eric Dumazet <edumazet@google.com> CC: Jamal Hadi Salim <jhs@mojatatu.com> Signed-off-by: John Fastabend <john.r.fastabend@intel.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Fastabend
David S. Miller
Родитель
a1ddcfee2d
Коммит
de5df63228
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@ -354,27 +354,53 @@ static int u32_init(struct tcf_proto *tp)
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return 0;
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}
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static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n)
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static int u32_destroy_key(struct tcf_proto *tp,
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struct tc_u_knode *n,
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bool free_pf)
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{
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tcf_unbind_filter(tp, &n->res);
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tcf_exts_destroy(tp, &n->exts);
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if (n->ht_down)
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n->ht_down->refcnt--;
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#ifdef CONFIG_CLS_U32_PERF
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free_percpu(n->pf);
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if (free_pf)
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free_percpu(n->pf);
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#endif
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#ifdef CONFIG_CLS_U32_MARK
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free_percpu(n->pcpu_success);
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if (free_pf)
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free_percpu(n->pcpu_success);
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#endif
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kfree(n);
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return 0;
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}
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/* u32_delete_key_rcu should be called when free'ing a copied
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* version of a tc_u_knode obtained from u32_init_knode(). When
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* copies are obtained from u32_init_knode() the statistics are
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* shared between the old and new copies to allow readers to
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* continue to update the statistics during the copy. To support
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* this the u32_delete_key_rcu variant does not free the percpu
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* statistics.
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*/
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static void u32_delete_key_rcu(struct rcu_head *rcu)
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{
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struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
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u32_destroy_key(key->tp, key);
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u32_destroy_key(key->tp, key, false);
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}
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/* u32_delete_key_freepf_rcu is the rcu callback variant
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* that free's the entire structure including the statistics
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* percpu variables. Only use this if the key is not a copy
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* returned by u32_init_knode(). See u32_delete_key_rcu()
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* for the variant that should be used with keys return from
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* u32_init_knode()
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*/
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static void u32_delete_key_freepf_rcu(struct rcu_head *rcu)
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{
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struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
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u32_destroy_key(key->tp, key, true);
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}
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static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
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@ -390,7 +416,7 @@ static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
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if (pkp == key) {
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RCU_INIT_POINTER(*kp, key->next);
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call_rcu(&key->rcu, u32_delete_key_rcu);
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call_rcu(&key->rcu, u32_delete_key_freepf_rcu);
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return 0;
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}
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}
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@ -408,7 +434,7 @@ static void u32_clear_hnode(struct tc_u_hnode *ht)
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while ((n = rtnl_dereference(ht->ht[h])) != NULL) {
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RCU_INIT_POINTER(ht->ht[h],
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rtnl_dereference(n->next));
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call_rcu(&n->rcu, u32_delete_key_rcu);
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call_rcu(&n->rcu, u32_delete_key_freepf_rcu);
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}
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}
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}
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@ -584,6 +610,82 @@ errout:
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return err;
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}
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static void u32_replace_knode(struct tcf_proto *tp,
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struct tc_u_common *tp_c,
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struct tc_u_knode *n)
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{
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struct tc_u_knode __rcu **ins;
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struct tc_u_knode *pins;
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struct tc_u_hnode *ht;
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if (TC_U32_HTID(n->handle) == TC_U32_ROOT)
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ht = rtnl_dereference(tp->root);
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else
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ht = u32_lookup_ht(tp_c, TC_U32_HTID(n->handle));
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ins = &ht->ht[TC_U32_HASH(n->handle)];
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/* The node must always exist for it to be replaced if this is not the
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* case then something went very wrong elsewhere.
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*/
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for (pins = rtnl_dereference(*ins); ;
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ins = &pins->next, pins = rtnl_dereference(*ins))
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if (pins->handle == n->handle)
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break;
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RCU_INIT_POINTER(n->next, pins->next);
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rcu_assign_pointer(*ins, n);
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}
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static struct tc_u_knode *u32_init_knode(struct tcf_proto *tp,
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struct tc_u_knode *n)
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{
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struct tc_u_knode *new;
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struct tc_u32_sel *s = &n->sel;
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new = kzalloc(sizeof(*n) + s->nkeys*sizeof(struct tc_u32_key),
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GFP_KERNEL);
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if (!new)
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return NULL;
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RCU_INIT_POINTER(new->next, n->next);
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new->handle = n->handle;
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RCU_INIT_POINTER(new->ht_up, n->ht_up);
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#ifdef CONFIG_NET_CLS_IND
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new->ifindex = n->ifindex;
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#endif
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new->fshift = n->fshift;
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new->res = n->res;
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RCU_INIT_POINTER(new->ht_down, n->ht_down);
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/* bump reference count as long as we hold pointer to structure */
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if (new->ht_down)
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new->ht_down->refcnt++;
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#ifdef CONFIG_CLS_U32_PERF
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/* Statistics may be incremented by readers during update
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* so we must keep them in tact. When the node is later destroyed
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* a special destroy call must be made to not free the pf memory.
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*/
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new->pf = n->pf;
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#endif
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#ifdef CONFIG_CLS_U32_MARK
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new->val = n->val;
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new->mask = n->mask;
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/* Similarly success statistics must be moved as pointers */
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new->pcpu_success = n->pcpu_success;
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#endif
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new->tp = tp;
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memcpy(&new->sel, s, sizeof(*s) + s->nkeys*sizeof(struct tc_u32_key));
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tcf_exts_init(&new->exts, TCA_U32_ACT, TCA_U32_POLICE);
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return new;
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}
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static int u32_change(struct net *net, struct sk_buff *in_skb,
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struct tcf_proto *tp, unsigned long base, u32 handle,
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struct nlattr **tca,
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@ -610,12 +712,27 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
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n = (struct tc_u_knode *)*arg;
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if (n) {
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struct tc_u_knode *new;
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if (TC_U32_KEY(n->handle) == 0)
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return -EINVAL;
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return u32_set_parms(net, tp, base,
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rtnl_dereference(n->ht_up), n, tb,
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tca[TCA_RATE], ovr);
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new = u32_init_knode(tp, n);
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if (!new)
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return -ENOMEM;
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err = u32_set_parms(net, tp, base,
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rtnl_dereference(n->ht_up), new, tb,
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tca[TCA_RATE], ovr);
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if (err) {
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u32_destroy_key(tp, new, false);
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return err;
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}
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u32_replace_knode(tp, tp_c, new);
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call_rcu(&n->rcu, u32_delete_key_rcu);
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return 0;
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}
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if (tb[TCA_U32_DIVISOR]) {
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