[PATCH v2] Bluetooth: hci_conn: Fix UAF in create_big_sync and create_big_complete

[PATCH v2] Bluetooth: hci_conn: Fix UAF in create_big_sync and create_big_complete

[Kai Zen]

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From kai.aizen.dev@gmail.com Mon Sep 17 00:00:00 2001
From: Kai Aizen <kai.aizen.dev@gmail.com>
Date: Wed, 4 Mar 2026 20:00:00 +0200
Subject: [PATCH v2] Bluetooth: hci_conn: Fix UAF in create_big_sync and
 create_big_complete

create_big_sync() and create_big_complete() are queued via
hci_cmd_sync_queue() with a raw hci_conn pointer as 'data', but unlike
all other hci_cmd_sync_queue() callbacks that receive an hci_conn pointer
they lack an hci_conn_valid() guard.

If the connection is torn down after the work is queued but before (or
during) execution, the work dereferences a freed hci_conn object.

Race path:
 1. hci_connect_bis() queues create_big_sync(conn) on hdev->req_workqueue
 2. ISO socket close() triggers hci_conn_drop(); for BIS_LINK timeo=0,
    disc_work fires immediately on hdev->workqueue
 3. disc_work -> hci_abort_conn -> hci_conn_del() frees conn
 4. create_big_sync() dequeued and runs on req_workqueue; conn is
    already freed -> slab-use-after-free

The two workqueues are distinct (req_workqueue vs workqueue). The only
lock held by create_big_sync is hci_req_sync_lock; the deletion path
in HCI event handlers holds only hci_dev_lock. No shared lock prevents
concurrent execution.

This is the same bug class fixed for hci_enhanced_setup_sync in commit
98ccd44002d8 ("Bluetooth: hci_conn: Fix UAF in hci_enhanced_setup_sync"),
and for hci_le_create_conn_sync, hci_le_pa_create_sync,
hci_le_big_create_sync, hci_acl_create_conn_sync. create_big_sync and
create_big_complete in hci_conn.c were not included in those sweeps.

Fix: add hci_conn_valid() guard at the start of both functions. In
create_big_sync the 'qos' pointer assignment is moved past the guard
to avoid dereferencing conn before validation.

Fixes: eca0ae4aea66 ("Bluetooth: Add initial implementation of BIS
connections")
Cc: stable@vger.kernel.org
Signed-off-by: Kai Aizen <kai.aizen.dev@gmail.com>
---
 net/bluetooth/hci_conn.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index a47f5daffdbf..e7fe9cc7a4a3 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -2119,10 +2119,15 @@
 static int create_big_sync(struct hci_dev *hdev, void *data)
 {
        struct hci_conn *conn = data;
-       struct bt_iso_qos *qos = &conn->iso_qos;
        u16 interval, sync_interval = 0;
        u32 flags = 0;
        int err;
+       struct bt_iso_qos *qos;
+
+       if (!hci_conn_valid(hdev, conn))
+               return -ECANCELED;
+
+       qos = &conn->iso_qos;

        if (qos->bcast.out.phys == BIT(1))
                flags |= MGMT_ADV_FLAG_SEC_2M;
@@ -2196,6 +2201,9 @@
 {
        struct hci_conn *conn = data;

+       if (!hci_conn_valid(hdev, conn))
+               return;
+
        bt_dev_dbg(hdev, "conn %p", conn);

        if (err) {

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[-- Attachment #2: 0001-v2-Bluetooth-hci_conn-Fix-UAF-in-create_big_sync.patch --]
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