6.12-stable review patch. If anyone has any objections, please let me know.

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From: Pauli Virtanen pav@iki.fi

[ Upstream commit 98454bc812f3611551e4b1f81732da4aa7b9597e ]

disconnect_all_peers() calls sleeping function (l2cap_chan_close) under spinlock. Holding the lock doesn't actually do any good -- we work on a local copy of the list, and the lock doesn't protect against peer->chan having already been freed.

Fix by taking refcounts of peer->chan instead. Clean up the code and old comments a bit.

Take devices_lock instead of RCU, because the kfree_rcu(); l2cap_chan_put(); construct in chan_close_cb() does not guarantee peer->chan is necessarily valid in RCU.

Also take l2cap_chan_lock() which is required for l2cap_chan_close().

Log: (bluez 6lowpan-tester Client Connect - Disable) ------ BUG: sleeping function called from invalid context at kernel/locking/mutex.c:575 ... <TASK> ... l2cap_send_disconn_req (net/bluetooth/l2cap_core.c:938 net/bluetooth/l2cap_core.c:1495) ... ? __pfx_l2cap_chan_close (net/bluetooth/l2cap_core.c:809) do_enable_set (net/bluetooth/6lowpan.c:1048 net/bluetooth/6lowpan.c:1068) ------

Fixes: 90305829635d ("Bluetooth: 6lowpan: Converting rwlocks to use RCU") Signed-off-by: Pauli Virtanen pav@iki.fi Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/bluetooth/6lowpan.c | 68 ++++++++++++++++++++++++++--------------- 1 file changed, 43 insertions(+), 25 deletions(-)

diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c index 73fe151a52a12..e5186a438290a 100644 --- a/net/bluetooth/6lowpan.c +++ b/net/bluetooth/6lowpan.c @@ -52,6 +52,11 @@ static bool enable_6lowpan; static struct l2cap_chan *listen_chan; static DEFINE_MUTEX(set_lock);

+enum { + LOWPAN_PEER_CLOSING, + LOWPAN_PEER_MAXBITS +}; + struct lowpan_peer { struct list_head list; struct rcu_head rcu; @@ -60,6 +65,8 @@ struct lowpan_peer { /* peer addresses in various formats */ unsigned char lladdr[ETH_ALEN]; struct in6_addr peer_addr; + + DECLARE_BITMAP(flags, LOWPAN_PEER_MAXBITS); };

struct lowpan_btle_dev { @@ -1013,41 +1020,52 @@ static int get_l2cap_conn(char *buf, bdaddr_t *addr, u8 *addr_type, static void disconnect_all_peers(void) { struct lowpan_btle_dev *entry; - struct lowpan_peer *peer, *tmp_peer, *new_peer; - struct list_head peers; - - INIT_LIST_HEAD(&peers); + struct lowpan_peer *peer; + int nchans;

- /* We make a separate list of peers as the close_cb() will - * modify the device peers list so it is better not to mess - * with the same list at the same time. + /* l2cap_chan_close() cannot be called from RCU, and lock ordering + * chan->lock > devices_lock prevents taking write side lock, so copy + * then close. */

rcu_read_lock(); + list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) + list_for_each_entry_rcu(peer, &entry->peers, list) + clear_bit(LOWPAN_PEER_CLOSING, peer->flags); + rcu_read_unlock();

- list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) { - list_for_each_entry_rcu(peer, &entry->peers, list) { - new_peer = kmalloc(sizeof(*new_peer), GFP_ATOMIC); - if (!new_peer) - break; + do { + struct l2cap_chan *chans[32]; + int i;

- new_peer->chan = peer->chan; - INIT_LIST_HEAD(&new_peer->list); + nchans = 0;

- list_add(&new_peer->list, &peers); - } - } + spin_lock(&devices_lock);

- rcu_read_unlock(); + list_for_each_entry_rcu(entry, &bt_6lowpan_devices, list) { + list_for_each_entry_rcu(peer, &entry->peers, list) { + if (test_and_set_bit(LOWPAN_PEER_CLOSING, + peer->flags)) + continue;

- spin_lock(&devices_lock); - list_for_each_entry_safe(peer, tmp_peer, &peers, list) { - l2cap_chan_close(peer->chan, ENOENT); + l2cap_chan_hold(peer->chan); + chans[nchans++] = peer->chan;

- list_del_rcu(&peer->list); - kfree_rcu(peer, rcu); - } - spin_unlock(&devices_lock); + if (nchans >= ARRAY_SIZE(chans)) + goto done; + } + } + +done: + spin_unlock(&devices_lock); + + for (i = 0; i < nchans; ++i) { + l2cap_chan_lock(chans[i]); + l2cap_chan_close(chans[i], ENOENT); + l2cap_chan_unlock(chans[i]); + l2cap_chan_put(chans[i]); + } + } while (nchans); }

struct set_enable {