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While the lock is dropped, the connection can be torn down under the same socket lock: iso_disconn_cfm() -> iso_conn_del() -> iso_chan_del() sets iso_pi(sk)->conn to NULL (and the broadcast teardown path can also clear conn->hcon on its own). When iso_conn_big_sync() re-acquires the lock and reads conn->hcon, conn may be NULL, causing a NULL pointer dereference (hcon is the first member of struct iso_conn). This path is reached from iso_sock_recvmsg() for a PA-sync broadcast sink socket (BT_SK_DEFER_SETUP | BT_SK_PA_SYNC), so the dropped-lock window can race with connection teardown driven by controller events. Re-validate iso_pi(sk)->conn and its hcon after re-acquiring the socket lock and bail out if the connection went away, as already done in the sibling iso_sock_rebind_bc(). Fixes: 7a17308c17880d ("Bluetooth: iso: Fix circular lock in iso_conn_big_sync") Cc: stable@vger.kernel.org Signed-off-by: Muhammad Bilal --- net/bluetooth/iso.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c index 3abd8111dda83..7186e8d88c757 100644 --- a/net/bluetooth/iso.c +++ b/net/bluetooth/iso.c @@ -1589,6 +1589,7 @@ static void iso_conn_big_sync(struct sock *sk) { int err; struct hci_dev *hdev; + struct iso_conn *conn; bdaddr_t src, dst; u8 src_type; @@ -1611,8 +1612,17 @@ static void iso_conn_big_sync(struct sock *sk) hci_dev_lock(hdev); lock_sock(sk); + /* The socket lock was dropped for hci_get_route(), so the connection + * may have been torn down meanwhile: iso_chan_del() clears conn and + * the broadcast teardown path can clear conn->hcon on its own. Check + * both before dereferencing conn->hcon. + */ + conn = iso_pi(sk)->conn; + if (!conn || !conn->hcon) + goto unlock; + if (!test_and_set_bit(BT_SK_BIG_SYNC, &iso_pi(sk)->flags)) { - err = hci_conn_big_create_sync(hdev, iso_pi(sk)->conn->hcon, + err = hci_conn_big_create_sync(hdev, conn->hcon, &iso_pi(sk)->qos, iso_pi(sk)->sync_handle, iso_pi(sk)->bc_num_bis, @@ -1621,6 +1631,7 @@ static void iso_conn_big_sync(struct sock *sk) bt_dev_err(hdev, "hci_big_create_sync: %d", err); } +unlock: release_sock(sk); hci_dev_unlock(hdev); hci_dev_put(hdev); -- 2.54.0