[PATCH 6.1.y] Bluetooth: hci_conn: fix potential UAF in create_big_sync

[ Upstream commit 0beddb0c380bed5f5b8e61ddbe14635bb73d0b41 ]

Add hci_conn_valid() check in create_big_sync() to detect stale
connections before proceeding with BIG creation. Handle the
resulting -ECANCELED in create_big_complete() and re-validate the
connection under hci_dev_lock() before dereferencing, matching the
pattern used by create_le_conn_complete() and create_pa_complete().

Keep the hci_conn object alive across the async boundary by taking
a reference via hci_conn_get() when queueing create_big_sync(), and
dropping it in the completion callback. The refcount and the lock
are complementary: the refcount keeps the object allocated, while
hci_dev_lock() serializes hci_conn_hash_del()'s list_del_rcu() on
hdev->conn_hash, as required by hci_conn_del().

hci_conn_put() is called outside hci_dev_unlock() so the final put
(which resolves to kfree() via bt_link_release) does not run under
hdev->lock, though the release path would be safe either way.

Without this, create_big_complete() would unconditionally
dereference the conn pointer on error, causing a use-after-free
via hci_connect_cfm() and hci_conn_del().

Fixes: eca0ae4aea66 ("Bluetooth: Add initial implementation of BIS connections")
Cc: [email protected]
Co-developed-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: David Carlier <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
[ kept stable's `qos->bcast.out.phy == 0x02` context line instead of upstream's renamed `qos->bcast.out.phys == BIT(1)` ]
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
[ Backported to 6.1.y: included inline helper hci_conn_valid() in
  include/net/bluetooth/hci_core.h from upstream commit 881559af5f5c ]
Signed-off-by: Todd Kjos <[email protected]>
---
 include/net/bluetooth/hci_core.h | 18 ++++++++++++++++++
 net/bluetooth/hci_conn.c         | 19 ++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index e67b1e5e0d2c8fb3c49696dd73e5fd6753412155..76764d399b23eff885e307148391c9cba5c6a4d0 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -1069,6 +1069,24 @@ static inline unsigned int hci_conn_count(struct hci_dev *hdev)
 	return c->acl_num + c->amp_num + c->sco_num + c->le_num + c->iso_num;
 }
 
+static inline bool hci_conn_valid(struct hci_dev *hdev, struct hci_conn *conn)
+{
+	struct hci_conn_hash *h = &hdev->conn_hash;
+	struct hci_conn  *c;
+
+	rcu_read_lock();
+
+	list_for_each_entry_rcu(c, &h->list, list) {
+		if (c == conn) {
+			rcu_read_unlock();
+			return true;
+		}
+	}
+	rcu_read_unlock();
+
+	return false;
+}
+
 static inline __u8 hci_conn_lookup_type(struct hci_dev *hdev, __u16 handle)
 {
 	struct hci_conn_hash *h = &hdev->conn_hash;
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 54cfcab7636380a2ced55986a81b0240e9d48d87..aa5404412cbd34320f00954bda71dce65910793c 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -2088,6 +2088,9 @@ static int create_big_sync(struct hci_dev *hdev, void *data)
 	u32 flags = 0;
 	int err;
 
+	if (!hci_conn_valid(hdev, conn))
+		return -ECANCELED;
+
 	if (qos->out.phy == 0x02)
 		flags |= MGMT_ADV_FLAG_SEC_2M;
 
@@ -2194,11 +2197,24 @@ static void create_big_complete(struct hci_dev *hdev, void *data, int err)
 
 	bt_dev_dbg(hdev, "conn %p", conn);
 
+	if (err == -ECANCELED)
+		goto done;
+
+	hci_dev_lock(hdev);
+
+	if (!hci_conn_valid(hdev, conn))
+		goto unlock;
+
 	if (err) {
 		bt_dev_err(hdev, "Unable to create BIG: %d", err);
 		hci_connect_cfm(conn, err);
 		hci_conn_del(conn);
 	}
+
+unlock:
+	hci_dev_unlock(hdev);
+done:
+	hci_conn_put(conn);
 }
 
 struct hci_conn *hci_connect_bis(struct hci_dev *hdev, bdaddr_t *dst,
@@ -2223,10 +2239,11 @@ struct hci_conn *hci_connect_bis(struct hci_dev *hdev, bdaddr_t *dst,
 	}
 
 	/* Queue start periodic advertising and create BIG */
-	err = hci_cmd_sync_queue(hdev, create_big_sync, conn,
+	err = hci_cmd_sync_queue(hdev, create_big_sync, hci_conn_get(conn),
 				 create_big_complete);
 	if (err < 0) {
 		hci_conn_drop(conn);
+		hci_conn_put(conn);
 		return ERR_PTR(err);
 	}
 
-- 
2.55.0.654.g21b8a5bc05-goog