From bc39a094730ce062fa034a529c93147c096cb488 Mon Sep 17 00:00:00 2001 From: hkbinbin Date: Tue, 31 Mar 2026 05:39:16 +0000 Subject: [PATCH] Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit hci_le_big_create_sync() uses DEFINE_FLEX to allocate a struct hci_cp_le_big_create_sync on the stack with room for 0x11 (17) BIS entries. However, conn->num_bis can hold up to HCI_MAX_ISO_BIS (31) entries — validated against ISO_MAX_NUM_BIS (0x1f) in the caller hci_conn_big_create_sync(). When conn->num_bis is between 18 and 31, the memcpy that copies conn->bis into cp->bis writes up to 14 bytes past the stack buffer, corrupting adjacent stack memory. This is trivially reproducible: binding an ISO socket with bc_num_bis = ISO_MAX_NUM_BIS (31) and calling listen() will eventually trigger hci_le_big_create_sync() from the HCI command sync worker, causing a KASAN-detectable stack-out-of-bounds write: BUG: KASAN: stack-out-of-bounds in hci_le_big_create_sync+0x256/0x3b0 Write of size 31 at addr ffffc90000487b48 by task kworker/u9:0/71 Fix this by changing the DEFINE_FLEX count from the incorrect 0x11 to HCI_MAX_ISO_BIS, which matches the maximum number of BIS entries that conn->bis can actually carry. Fixes: 42ecf1947135 ("Bluetooth: ISO: Do not emit LE BIG Create Sync if previous is pending") Cc: stable@vger.kernel.org Signed-off-by: hkbinbin Reviewed-by: Paul Menzel Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/hci_sync.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c index ffb0ceda6f7b..919ec275dd23 100644 --- a/net/bluetooth/hci_sync.c +++ b/net/bluetooth/hci_sync.c @@ -7241,7 +7241,8 @@ static void create_big_complete(struct hci_dev *hdev, void *data, int err) static int hci_le_big_create_sync(struct hci_dev *hdev, void *data) { - DEFINE_FLEX(struct hci_cp_le_big_create_sync, cp, bis, num_bis, 0x11); + DEFINE_FLEX(struct hci_cp_le_big_create_sync, cp, bis, num_bis, + HCI_MAX_ISO_BIS); struct hci_conn *conn = data; struct bt_iso_qos *qos = &conn->iso_qos; int err;