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authorDaniel Borkmann <daniel@iogearbox.net>2015-07-29 23:35:25 +0200
committerDavid S. Miller <davem@davemloft.net>2015-07-30 14:20:39 -0700
commit28e6b67f0b292f557468c139085303b15f1a678f (patch)
treea50641ae4b95168a1b64a423d612bc027b982817 /net
parent990c9b347245ef0d5df1c70659df68e7e9ba6a72 (diff)
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net: sched: fix refcount imbalance in actions
Since commit 55334a5db5cd ("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 55334a5db5cd 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: 55334a5db5cd ("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>
Diffstat (limited to 'net')
-rw-r--r--net/sched/act_api.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index af427a3dbcba..43ec92680ae8 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -45,7 +45,7 @@ void tcf_hash_destroy(struct tc_action *a)
}
EXPORT_SYMBOL(tcf_hash_destroy);
-int tcf_hash_release(struct tc_action *a, int bind)
+int __tcf_hash_release(struct tc_action *a, bool bind, bool strict)
{
struct tcf_common *p = a->priv;
int ret = 0;
@@ -53,7 +53,7 @@ int tcf_hash_release(struct tc_action *a, int bind)
if (p) {
if (bind)
p->tcfc_bindcnt--;
- else if (p->tcfc_bindcnt > 0)
+ else if (strict && p->tcfc_bindcnt > 0)
return -EPERM;
p->tcfc_refcnt--;
@@ -64,9 +64,10 @@ int tcf_hash_release(struct tc_action *a, int bind)
ret = 1;
}
}
+
return ret;
}
-EXPORT_SYMBOL(tcf_hash_release);
+EXPORT_SYMBOL(__tcf_hash_release);
static int tcf_dump_walker(struct sk_buff *skb, struct netlink_callback *cb,
struct tc_action *a)
@@ -136,7 +137,7 @@ static int tcf_del_walker(struct sk_buff *skb, struct tc_action *a)
head = &hinfo->htab[tcf_hash(i, hinfo->hmask)];
hlist_for_each_entry_safe(p, n, head, tcfc_head) {
a->priv = p;
- ret = tcf_hash_release(a, 0);
+ ret = __tcf_hash_release(a, false, true);
if (ret == ACT_P_DELETED) {
module_put(a->ops->owner);
n_i++;
@@ -408,7 +409,7 @@ int tcf_action_destroy(struct list_head *actions, int bind)
int ret = 0;
list_for_each_entry_safe(a, tmp, actions, list) {
- ret = tcf_hash_release(a, bind);
+ ret = __tcf_hash_release(a, bind, true);
if (ret == ACT_P_DELETED)
module_put(a->ops->owner);
else if (ret < 0)