[PATCH 4.9 095/108] tipc: add subscription refcount to avoid invalid delete

Greg Kroah-Hartman
2017-06-15T18:00:49Z

From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>

[ Upstream commit d094c4d5f5c7e1b225e94227ca3f007be3adc4e8 ]

Until now, the subscribers keep track of the subscriptions using
reference count at subscriber level. At subscription cancel or
subscriber delete, we delete the subscription only if the timer
was pending for the subscription. This approach is incorrect as:
1. del_timer() is not SMP safe, if on CPU0 the check for pending
timer returns true but CPU1 might schedule the timer callback
thereby deleting the subscription. Thus when CPU0 is scheduled,
it deletes an invalid subscription.
2. We export tipc_subscrp_report_overlap(), which accesses the
subscription pointer multiple times. Meanwhile the subscription
timer can expire thereby freeing the subscription and we might
continue to access the subscription pointer leading to memory
violations.

In this commit, we introduce subscription refcount to avoid deleting
an invalid subscription.

Reported-and-Tested-by: John Thompson <thompa.atl@gmail.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/tipc/subscr.c | 124 ++++++++++++++++++++++++++++++------------------------
net/tipc/subscr.h | 1
2 files changed, 71 insertions(+), 54 deletions(-)

--- a/net/tipc/subscr.c
+++ b/net/tipc/subscr.c
@@ -54,6 +54,8 @@ struct tipc_subscriber {

static void tipc_subscrp_delete(struct tipc_subscription *sub);
static void tipc_subscrb_put(struct tipc_subscriber *subscriber);
+static void tipc_subscrp_put(struct tipc_subscription *subscription);
+static void tipc_subscrp_get(struct tipc_subscription *subscription);

/**
* htohl - convert value to endianness used by destination
@@ -123,6 +125,7 @@ void tipc_subscrp_report_overlap(struct
{
struct tipc_name_seq seq;

+ tipc_subscrp_get(sub);
tipc_subscrp_convert_seq(&sub->evt.s.seq, sub->swap, &seq);
if (!tipc_subscrp_check_overlap(&seq, found_lower, found_upper))
return;
@@ -132,30 +135,23 @@ void tipc_subscrp_report_overlap(struct

tipc_subscrp_send_event(sub, found_lower, found_upper, event, port_ref,
node);
+ tipc_subscrp_put(sub);
}

static void tipc_subscrp_timeout(unsigned long data)
{
struct tipc_subscription *sub = (struct tipc_subscription *)data;
- struct tipc_subscriber *subscriber = sub->subscriber;

/* Notify subscriber of timeout */
tipc_subscrp_send_event(sub, sub->evt.s.seq.lower, sub->evt.s.seq.upper,
TIPC_SUBSCR_TIMEOUT, 0, 0);

- spin_lock_bh(&subscriber->lock);
- tipc_subscrp_delete(sub);
- spin_unlock_bh(&subscriber->lock);
-
- tipc_subscrb_put(subscriber);
+ tipc_subscrp_put(sub);
}

static void tipc_subscrb_kref_release(struct kref *kref)
{
- struct tipc_subscriber *subcriber = container_of(kref,
- struct tipc_subscriber, kref);
-
- kfree(subcriber);
+ kfree(container_of(kref,struct tipc_subscriber, kref));
}

static void tipc_subscrb_put(struct tipc_subscriber *subscriber)
@@ -168,6 +164,59 @@ static void tipc_subscrb_get(struct tipc
kref_get(&subscriber->kref);
}

+static void tipc_subscrp_kref_release(struct kref *kref)
+{
+ struct tipc_subscription *sub = container_of(kref,
+ struct tipc_subscription,
+ kref);
+ struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
+ struct tipc_subscriber *subscriber = sub->subscriber;
+
+ spin_lock_bh(&subscriber->lock);
+ tipc_nametbl_unsubscribe(sub);
+ list_del(&sub->subscrp_list);
+ atomic_dec(&tn->subscription_count);
+ spin_unlock_bh(&subscriber->lock);
+ kfree(sub);
+ tipc_subscrb_put(subscriber);
+}
+
+static void tipc_subscrp_put(struct tipc_subscription *subscription)
+{
+ kref_put(&subscription->kref, tipc_subscrp_kref_release);
+}
+
+static void tipc_subscrp_get(struct tipc_subscription *subscription)
+{
+ kref_get(&subscription->kref);
+}
+
+/* tipc_subscrb_subscrp_delete - delete a specific subscription or all
+ * subscriptions for a given subscriber.
+ */
+static void tipc_subscrb_subscrp_delete(struct tipc_subscriber *subscriber,
+ struct tipc_subscr *s)
+{
+ struct list_head *subscription_list = &subscriber->subscrp_list;
+ struct tipc_subscription *sub, *temp;
+
+ spin_lock_bh(&subscriber->lock);
+ list_for_each_entry_safe(sub, temp, subscription_list, subscrp_list) {
+ if (s && memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr)))
+ continue;
+
+ tipc_subscrp_get(sub);
+ spin_unlock_bh(&subscriber->lock);
+ tipc_subscrp_delete(sub);
+ tipc_subscrp_put(sub);
+ spin_lock_bh(&subscriber->lock);
+
+ if (s)
+ break;
+ }
+ spin_unlock_bh(&subscriber->lock);
+}
+
static struct tipc_subscriber *tipc_subscrb_create(int conid)
{
struct tipc_subscriber *subscriber;
@@ -177,8 +226,8 @@ static struct tipc_subscriber *tipc_subs
pr_warn("Subscriber rejected, no memory\n");
return NULL;
}
- kref_init(&subscriber->kref);
INIT_LIST_HEAD(&subscriber->subscrp_list);
+ kref_init(&subscriber->kref);
subscriber->conid = conid;
spin_lock_init(&subscriber->lock);

@@ -187,55 +236,22 @@ static struct tipc_subscriber *tipc_subs

static void tipc_subscrb_delete(struct tipc_subscriber *subscriber)
{
- struct tipc_subscription *sub, *temp;
- u32 timeout;
-
- spin_lock_bh(&subscriber->lock);
- /* Destroy any existing subscriptions for subscriber */
- list_for_each_entry_safe(sub, temp, &subscriber->subscrp_list,
- subscrp_list) {
- timeout = htohl(sub->evt.s.timeout, sub->swap);
- if ((timeout == TIPC_WAIT_FOREVER) || del_timer(&sub->timer)) {
- tipc_subscrp_delete(sub);
- tipc_subscrb_put(subscriber);
- }
- }
- spin_unlock_bh(&subscriber->lock);
-
+ tipc_subscrb_subscrp_delete(subscriber, NULL);
tipc_subscrb_put(subscriber);
}

static void tipc_subscrp_delete(struct tipc_subscription *sub)
{
- struct tipc_net *tn = net_generic(sub->net, tipc_net_id);
+ u32 timeout = htohl(sub->evt.s.timeout, sub->swap);

- tipc_nametbl_unsubscribe(sub);
- list_del(&sub->subscrp_list);
- kfree(sub);
- atomic_dec(&tn->subscription_count);
+ if (timeout == TIPC_WAIT_FOREVER || del_timer(&sub->timer))
+ tipc_subscrp_put(sub);
}

static void tipc_subscrp_cancel(struct tipc_subscr *s,
struct tipc_subscriber *subscriber)
{
- struct tipc_subscription *sub, *temp;
- u32 timeout;
-
- spin_lock_bh(&subscriber->lock);
- /* Find first matching subscription, exit if not found */
- list_for_each_entry_safe(sub, temp, &subscriber->subscrp_list,
- subscrp_list) {
- if (!memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr))) {
- timeout = htohl(sub->evt.s.timeout, sub->swap);
- if ((timeout == TIPC_WAIT_FOREVER) ||
- del_timer(&sub->timer)) {
- tipc_subscrp_delete(sub);
- tipc_subscrb_put(subscriber);
- }
- break;
- }
- }
- spin_unlock_bh(&subscriber->lock);
+ tipc_subscrb_subscrp_delete(subscriber, s);
}

static struct tipc_subscription *tipc_subscrp_create(struct net *net,
@@ -272,6 +288,7 @@ static struct tipc_subscription *tipc_su
sub->swap = swap;
memcpy(&sub->evt.s, s, sizeof(*s));
atomic_inc(&tn->subscription_count);
+ kref_init(&sub->kref);
return sub;
}

@@ -288,17 +305,16 @@ static void tipc_subscrp_subscribe(struc

spin_lock_bh(&subscriber->lock);
list_add(&sub->subscrp_list, &subscriber->subscrp_list);
- tipc_subscrb_get(subscriber);
sub->subscriber = subscriber;
tipc_nametbl_subscribe(sub);
+ tipc_subscrb_get(subscriber);
spin_unlock_bh(&subscriber->lock);

+ setup_timer(&sub->timer, tipc_subscrp_timeout, (unsigned long)sub);
timeout = htohl(sub->evt.s.timeout, swap);
- if (timeout == TIPC_WAIT_FOREVER)
- return;

- setup_timer(&sub->timer, tipc_subscrp_timeout, (unsigned long)sub);
- mod_timer(&sub->timer, jiffies + msecs_to_jiffies(timeout));
+ if (timeout != TIPC_WAIT_FOREVER)
+ mod_timer(&sub->timer, jiffies + msecs_to_jiffies(timeout));
}

/* Handle one termination request for the subscriber */
--- a/net/tipc/subscr.h
+++ b/net/tipc/subscr.h
@@ -57,6 +57,7 @@ struct tipc_subscriber;
* @evt: template for events generated by subscription
*/
struct tipc_subscription {
+ struct kref kref;
struct tipc_subscriber *subscriber;
struct net *net;
struct timer_list timer;