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linux/include/net/act_api.h
Daniel Borkmann 28e6b67f0b net: sched: fix refcount imbalance in actions 
Since commit 55334a5db5 ("net_sched: act: refuse to remove bound action
outside"), we end up with a wrong reference count for a tc action.

Test case 1:

  FOO="1,6 0 0 4294967295,"
  BAR="1,6 0 0 4294967294,"
  tc filter add dev foo parent 1: bpf bytecode "$FOO" flowid 1:1 \
     action bpf bytecode "$FOO"
  tc actions show action bpf
    action order 0: bpf bytecode '1,6 0 0 4294967295' default-action pipe
    index 1 ref 1 bind 1
  tc actions replace action bpf bytecode "$BAR" index 1
  tc actions show action bpf
    action order 0: bpf bytecode '1,6 0 0 4294967294' default-action pipe
    index 1 ref 2 bind 1
  tc actions replace action bpf bytecode "$FOO" index 1
  tc actions show action bpf
    action order 0: bpf bytecode '1,6 0 0 4294967295' default-action pipe
    index 1 ref 3 bind 1

Test case 2:

  FOO="1,6 0 0 4294967295,"
  tc filter add dev foo parent 1: bpf bytecode "$FOO" flowid 1:1 action ok
  tc actions show action gact
    action order 0: gact action pass
    random type none pass val 0
     index 1 ref 1 bind 1
  tc actions add action drop index 1
    RTNETLINK answers: File exists [...]
  tc actions show action gact
    action order 0: gact action pass
     random type none pass val 0
     index 1 ref 2 bind 1
  tc actions add action drop index 1
    RTNETLINK answers: File exists [...]
  tc actions show action gact
    action order 0: gact action pass
     random type none pass val 0
     index 1 ref 3 bind 1

What happens is that in tcf_hash_check(), we check tcf_common for a given
index and increase tcfc_refcnt and conditionally tcfc_bindcnt when we've
found an existing action. Now there are the following cases:

  1) We do a late binding of an action. In that case, we leave the
     tcfc_refcnt/tcfc_bindcnt increased and are done with the ->init()
     handler. This is correctly handeled.

  2) We replace the given action, or we try to add one without replacing
     and find out that the action at a specific index already exists
     (thus, we go out with error in that case).

In case of 2), we have to undo the reference count increase from
tcf_hash_check() in the tcf_hash_check() function. Currently, we fail to
do so because of the 'tcfc_bindcnt > 0' check which bails out early with
an -EPERM error.

Now, while commit 55334a5db5 prevents 'tc actions del action ...' on an
already classifier-bound action to drop the reference count (which could
then become negative, wrap around etc), this restriction only accounts for
invocations outside a specific action's ->init() handler.

One possible solution would be to add a flag thus we possibly trigger
the -EPERM ony in situations where it is indeed relevant.

After the patch, above test cases have correct reference count again.

Fixes: 55334a5db5 ("net_sched: act: refuse to remove bound action outside")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-07-30 14:20:39 -07:00

133 lines
3.9 KiB
C
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#ifndef __NET_ACT_API_H
#define __NET_ACT_API_H
/*
* Public police action API for classifiers/qdiscs
*/
#include <net/sch_generic.h>
#include <net/pkt_sched.h>
struct tcf_common {
struct hlist_node tcfc_head;
u32 tcfc_index;
int tcfc_refcnt;
int tcfc_bindcnt;
u32 tcfc_capab;
int tcfc_action;
struct tcf_t tcfc_tm;
struct gnet_stats_basic_packed tcfc_bstats;
struct gnet_stats_queue tcfc_qstats;
struct gnet_stats_rate_est64 tcfc_rate_est;
spinlock_t tcfc_lock;
struct rcu_head tcfc_rcu;
};
#define tcf_head common.tcfc_head
#define tcf_index common.tcfc_index
#define tcf_refcnt common.tcfc_refcnt
#define tcf_bindcnt common.tcfc_bindcnt
#define tcf_capab common.tcfc_capab
#define tcf_action common.tcfc_action
#define tcf_tm common.tcfc_tm
#define tcf_bstats common.tcfc_bstats
#define tcf_qstats common.tcfc_qstats
#define tcf_rate_est common.tcfc_rate_est
#define tcf_lock common.tcfc_lock
#define tcf_rcu common.tcfc_rcu
struct tcf_hashinfo {
struct hlist_head *htab;
unsigned int hmask;
spinlock_t lock;
u32 index;
};
static inline unsigned int tcf_hash(u32 index, unsigned int hmask)
{
return index & hmask;
}
static inline int tcf_hashinfo_init(struct tcf_hashinfo *hf, unsigned int mask)
{
int i;
spin_lock_init(&hf->lock);
hf->index = 0;
hf->hmask = mask;
hf->htab = kzalloc((mask + 1) * sizeof(struct hlist_head),
GFP_KERNEL);
if (!hf->htab)
return -ENOMEM;
for (i = 0; i < mask + 1; i++)
INIT_HLIST_HEAD(&hf->htab[i]);
return 0;
}
static inline void tcf_hashinfo_destroy(struct tcf_hashinfo *hf)
{
kfree(hf->htab);
}
#ifdef CONFIG_NET_CLS_ACT
#define ACT_P_CREATED 1
#define ACT_P_DELETED 1
struct tc_action {
void *priv;
const struct tc_action_ops *ops;
__u32 type; /* for backward compat(TCA_OLD_COMPAT) */
__u32 order;
struct list_head list;
};
struct tc_action_ops {
struct list_head head;
struct tcf_hashinfo *hinfo;
char kind[IFNAMSIZ];
__u32 type; /* TBD to match kind */
struct module *owner;
int (*act)(struct sk_buff *, const struct tc_action *, struct tcf_result *);
int (*dump)(struct sk_buff *, struct tc_action *, int, int);
void (*cleanup)(struct tc_action *, int bind);
int (*lookup)(struct tc_action *, u32);
int (*init)(struct net *net, struct nlattr *nla,
struct nlattr *est, struct tc_action *act, int ovr,
int bind);
int (*walk)(struct sk_buff *, struct netlink_callback *, int, struct tc_action *);
};
int tcf_hash_search(struct tc_action *a, u32 index);
void tcf_hash_destroy(struct tc_action *a);
u32 tcf_hash_new_index(struct tcf_hashinfo *hinfo);
int tcf_hash_check(u32 index, struct tc_action *a, int bind);
int tcf_hash_create(u32 index, struct nlattr *est, struct tc_action *a,
int size, int bind);
void tcf_hash_cleanup(struct tc_action *a, struct nlattr *est);
void tcf_hash_insert(struct tc_action *a);
int __tcf_hash_release(struct tc_action *a, bool bind, bool strict);
static inline int tcf_hash_release(struct tc_action *a, bool bind)
{
return __tcf_hash_release(a, bind, false);
}
int tcf_register_action(struct tc_action_ops *a, unsigned int mask);
int tcf_unregister_action(struct tc_action_ops *a);
int tcf_action_destroy(struct list_head *actions, int bind);
int tcf_action_exec(struct sk_buff *skb, const struct list_head *actions,
struct tcf_result *res);
int tcf_action_init(struct net *net, struct nlattr *nla,
struct nlattr *est, char *n, int ovr,
int bind, struct list_head *);
struct tc_action *tcf_action_init_1(struct net *net, struct nlattr *nla,
struct nlattr *est, char *n, int ovr,
int bind);
int tcf_action_dump(struct sk_buff *skb, struct list_head *, int, int);
int tcf_action_dump_old(struct sk_buff *skb, struct tc_action *a, int, int);
int tcf_action_dump_1(struct sk_buff *skb, struct tc_action *a, int, int);
int tcf_action_copy_stats(struct sk_buff *, struct tc_action *, int);
#endif /* CONFIG_NET_CLS_ACT */
#endif
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