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Subject[PATCH 4.19 040/276] batman-adv: mcast: fix multicast tt/tvlv worker locking
Date
From: Linus Lüssing <linus.luessing@c0d3.blue>

commit a3c7cd0cdf1107f891aff847ad481e34df727055 upstream.

Syzbot has reported some issues with the locking assumptions made for
the multicast tt/tvlv worker: It was able to trigger the WARN_ON() in
batadv_mcast_mla_tt_retract() and batadv_mcast_mla_tt_add().
While hard/not reproduceable for us so far it seems that the
delayed_work_pending() we use might not be quite safe from reordering.

Therefore this patch adds an explicit, new spinlock to protect the
update of the mla_list and flags in bat_priv and then removes the
WARN_ON(delayed_work_pending()).

Reported-by: syzbot+83f2d54ec6b7e417e13f@syzkaller.appspotmail.com
Reported-by: syzbot+050927a651272b145a5d@syzkaller.appspotmail.com
Reported-by: syzbot+979ffc89b87309b1b94b@syzkaller.appspotmail.com
Reported-by: syzbot+f9f3f388440283da2965@syzkaller.appspotmail.com
Fixes: cbebd363b2e9 ("batman-adv: Use own timer for multicast TT and TVLV updates")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/batman-adv/main.c | 1 +
net/batman-adv/multicast.c | 11 +++--------
net/batman-adv/types.h | 5 +++++
3 files changed, 9 insertions(+), 8 deletions(-)

--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -160,6 +160,7 @@ int batadv_mesh_init(struct net_device *
spin_lock_init(&bat_priv->tt.commit_lock);
spin_lock_init(&bat_priv->gw.list_lock);
#ifdef CONFIG_BATMAN_ADV_MCAST
+ spin_lock_init(&bat_priv->mcast.mla_lock);
spin_lock_init(&bat_priv->mcast.want_lists_lock);
#endif
spin_lock_init(&bat_priv->tvlv.container_list_lock);
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -325,8 +325,6 @@ static void batadv_mcast_mla_list_free(s
* translation table except the ones listed in the given mcast_list.
*
* If mcast_list is NULL then all are retracted.
- *
- * Do not call outside of the mcast worker! (or cancel mcast worker first)
*/
static void batadv_mcast_mla_tt_retract(struct batadv_priv *bat_priv,
struct hlist_head *mcast_list)
@@ -334,8 +332,6 @@ static void batadv_mcast_mla_tt_retract(
struct batadv_hw_addr *mcast_entry;
struct hlist_node *tmp;

- WARN_ON(delayed_work_pending(&bat_priv->mcast.work));
-
hlist_for_each_entry_safe(mcast_entry, tmp, &bat_priv->mcast.mla_list,
list) {
if (mcast_list &&
@@ -359,8 +355,6 @@ static void batadv_mcast_mla_tt_retract(
*
* Adds multicast listener announcements from the given mcast_list to the
* translation table if they have not been added yet.
- *
- * Do not call outside of the mcast worker! (or cancel mcast worker first)
*/
static void batadv_mcast_mla_tt_add(struct batadv_priv *bat_priv,
struct hlist_head *mcast_list)
@@ -368,8 +362,6 @@ static void batadv_mcast_mla_tt_add(stru
struct batadv_hw_addr *mcast_entry;
struct hlist_node *tmp;

- WARN_ON(delayed_work_pending(&bat_priv->mcast.work));
-
if (!mcast_list)
return;

@@ -658,7 +650,10 @@ static void batadv_mcast_mla_update(stru
priv_mcast = container_of(delayed_work, struct batadv_priv_mcast, work);
bat_priv = container_of(priv_mcast, struct batadv_priv, mcast);

+ spin_lock(&bat_priv->mcast.mla_lock);
__batadv_mcast_mla_update(bat_priv);
+ spin_unlock(&bat_priv->mcast.mla_lock);
+
batadv_mcast_start_timer(bat_priv);
}

--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -1216,6 +1216,11 @@ struct batadv_priv_mcast {
unsigned char bridged:1;

/**
+ * @mla_lock: a lock protecting mla_list and mla_flags
+ */
+ spinlock_t mla_lock;
+
+ /**
* @num_want_all_unsnoopables: number of nodes wanting unsnoopable IP
* traffic
*/

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