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Message-Id: <1441372118-5933-39-git-send-email-luis.henriques@canonical.com>
Date: Fri, 4 Sep 2015 14:07:06 +0100
From: Luis Henriques <luis.henriques@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Daniel Borkmann <daniel@...earbox.net>,
"David S. Miller" <davem@...emloft.net>,
Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 038/130] net: sched: fix refcount imbalance in actions
3.16.7-ckt17 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Daniel Borkmann <daniel@...earbox.net>
commit 28e6b67f0b292f557468c139085303b15f1a678f upstream.
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@...earbox.net>
Reviewed-by: Cong Wang <cwang@...pensource.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
include/net/act_api.h | 8 +++++++-
net/sched/act_api.c | 11 ++++++-----
2 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/include/net/act_api.h b/include/net/act_api.h
index 3ee4c92afd1b..931738bc5bba 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -99,7 +99,6 @@ struct tc_action_ops {
int tcf_hash_search(struct tc_action *a, u32 index);
void tcf_hash_destroy(struct tc_action *a);
-int tcf_hash_release(struct tc_action *a, int bind);
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,
@@ -107,6 +106,13 @@ int tcf_hash_create(u32 index, struct nlattr *est, struct tc_action *a,
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);
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 648778aef1a2..55307ccf4453 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++;
@@ -412,7 +413,7 @@ 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)
--
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