Commit de5df632 authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
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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: default avatarJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a1ddcfee
......@@ -354,27 +354,53 @@ static int u32_init(struct tcf_proto *tp)
return 0;
}
static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n)
static int u32_destroy_key(struct tcf_proto *tp,
struct tc_u_knode *n,
bool free_pf)
{
tcf_unbind_filter(tp, &n->res);
tcf_exts_destroy(tp, &n->exts);
if (n->ht_down)
n->ht_down->refcnt--;
#ifdef CONFIG_CLS_U32_PERF
free_percpu(n->pf);
if (free_pf)
free_percpu(n->pf);
#endif
#ifdef CONFIG_CLS_U32_MARK
free_percpu(n->pcpu_success);
if (free_pf)
free_percpu(n->pcpu_success);
#endif
kfree(n);
return 0;
}
/* u32_delete_key_rcu should be called when free'ing a copied
* version of a tc_u_knode obtained from u32_init_knode(). When
* copies are obtained from u32_init_knode() the statistics are
* shared between the old and new copies to allow readers to
* continue to update the statistics during the copy. To support
* this the u32_delete_key_rcu variant does not free the percpu
* statistics.
*/
static void u32_delete_key_rcu(struct rcu_head *rcu)
{
struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
u32_destroy_key(key->tp, key);
u32_destroy_key(key->tp, key, false);
}
/* u32_delete_key_freepf_rcu is the rcu callback variant
* that free's the entire structure including the statistics
* percpu variables. Only use this if the key is not a copy
* returned by u32_init_knode(). See u32_delete_key_rcu()
* for the variant that should be used with keys return from
* u32_init_knode()
*/
static void u32_delete_key_freepf_rcu(struct rcu_head *rcu)
{
struct tc_u_knode *key = container_of(rcu, struct tc_u_knode, rcu);
u32_destroy_key(key->tp, key, true);
}
static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
......@@ -390,7 +416,7 @@ static int u32_delete_key(struct tcf_proto *tp, struct tc_u_knode *key)
if (pkp == key) {
RCU_INIT_POINTER(*kp, key->next);
call_rcu(&key->rcu, u32_delete_key_rcu);
call_rcu(&key->rcu, u32_delete_key_freepf_rcu);
return 0;
}
}
......@@ -408,7 +434,7 @@ static void u32_clear_hnode(struct tc_u_hnode *ht)
while ((n = rtnl_dereference(ht->ht[h])) != NULL) {
RCU_INIT_POINTER(ht->ht[h],
rtnl_dereference(n->next));
call_rcu(&n->rcu, u32_delete_key_rcu);
call_rcu(&n->rcu, u32_delete_key_freepf_rcu);
}
}
}
......@@ -584,6 +610,82 @@ errout:
return err;
}
static void u32_replace_knode(struct tcf_proto *tp,
struct tc_u_common *tp_c,
struct tc_u_knode *n)
{
struct tc_u_knode __rcu **ins;
struct tc_u_knode *pins;
struct tc_u_hnode *ht;
if (TC_U32_HTID(n->handle) == TC_U32_ROOT)
ht = rtnl_dereference(tp->root);
else
ht = u32_lookup_ht(tp_c, TC_U32_HTID(n->handle));
ins = &ht->ht[TC_U32_HASH(n->handle)];
/* The node must always exist for it to be replaced if this is not the
* case then something went very wrong elsewhere.
*/
for (pins = rtnl_dereference(*ins); ;
ins = &pins->next, pins = rtnl_dereference(*ins))
if (pins->handle == n->handle)
break;
RCU_INIT_POINTER(n->next, pins->next);
rcu_assign_pointer(*ins, n);
}
static struct tc_u_knode *u32_init_knode(struct tcf_proto *tp,
struct tc_u_knode *n)
{
struct tc_u_knode *new;
struct tc_u32_sel *s = &n->sel;
new = kzalloc(sizeof(*n) + s->nkeys*sizeof(struct tc_u32_key),
GFP_KERNEL);
if (!new)
return NULL;
RCU_INIT_POINTER(new->next, n->next);
new->handle = n->handle;
RCU_INIT_POINTER(new->ht_up, n->ht_up);
#ifdef CONFIG_NET_CLS_IND
new->ifindex = n->ifindex;
#endif
new->fshift = n->fshift;
new->res = n->res;
RCU_INIT_POINTER(new->ht_down, n->ht_down);
/* bump reference count as long as we hold pointer to structure */
if (new->ht_down)
new->ht_down->refcnt++;
#ifdef CONFIG_CLS_U32_PERF
/* Statistics may be incremented by readers during update
* so we must keep them in tact. When the node is later destroyed
* a special destroy call must be made to not free the pf memory.
*/
new->pf = n->pf;
#endif
#ifdef CONFIG_CLS_U32_MARK
new->val = n->val;
new->mask = n->mask;
/* Similarly success statistics must be moved as pointers */
new->pcpu_success = n->pcpu_success;
#endif
new->tp = tp;
memcpy(&new->sel, s, sizeof(*s) + s->nkeys*sizeof(struct tc_u32_key));
tcf_exts_init(&new->exts, TCA_U32_ACT, TCA_U32_POLICE);
return new;
}
static int u32_change(struct net *net, struct sk_buff *in_skb,
struct tcf_proto *tp, unsigned long base, u32 handle,
struct nlattr **tca,
......@@ -610,12 +712,27 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
n = (struct tc_u_knode *)*arg;
if (n) {
struct tc_u_knode *new;
if (TC_U32_KEY(n->handle) == 0)
return -EINVAL;
return u32_set_parms(net, tp, base,
rtnl_dereference(n->ht_up), n, tb,
tca[TCA_RATE], ovr);
new = u32_init_knode(tp, n);
if (!new)
return -ENOMEM;
err = u32_set_parms(net, tp, base,
rtnl_dereference(n->ht_up), new, tb,
tca[TCA_RATE], ovr);
if (err) {
u32_destroy_key(tp, new, false);
return err;
}
u32_replace_knode(tp, tp_c, new);
call_rcu(&n->rcu, u32_delete_key_rcu);
return 0;
}
if (tb[TCA_U32_DIVISOR]) {
......
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