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[104.194.93.216]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2c3c747e410sm9271157eec.25.2026.03.30.22.39.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 22:39:24 -0700 (PDT) From: hkbinbin To: marcel@holtmann.org, luiz.dentz@gmail.com Cc: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, hkbinbin , stable@vger.kernel.org Subject: [PATCH] Bluetooth: hci_sync: fix stack buffer overflow in hci_le_big_create_sync Date: Tue, 31 Mar 2026 05:39:16 +0000 Message-ID: <20260331053916.1856760-1-hkbinbinbin@gmail.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 --- 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 45d16639874a..b84587061ae0 100644 --- a/net/bluetooth/hci_sync.c +++ b/net/bluetooth/hci_sync.c @@ -7222,7 +7222,8 @@ 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; -- 2.51.0