iso_sock_connect() checks the socket state before taking the socket lock and drops the lock again before setting up a connection. Two callers can both pass the admission check while the socket is open or bound. Caller A can copy its destination for route selection, then caller B can replace the socket destination before A binds or connects the CIS. A then uses B's destination with the route selected for its own request. B can also proceed after A attaches a connection and sets BT_CONNECT. For deferred BIS setup, B can bind a second BIS and overwrite iso_pi(sk)->conn, leaving the first connection's reference and conn->sk back-pointer stranded. Concurrent CIS connects can likewise replace the socket's connection. Later teardown only detaches the current connection, so a callback on the old connection can race with socket release and access a freed socket. KASAN reported: BUG: KASAN: slab-use-after-free in iso_sock_hold+0xf7/0x1b0 Call Trace: iso_sock_hold+0xf7/0x1b0 iso_conn_del+0x7b/0x1d0 iso_connect_cfm+0x186/0x16a0 hci_conn_failed+0x154/0x280 hci_abort_conn_sync+0x3dc/0x7d0 hci_cmd_sync_work+0x173/0x300 Allocated by task 121: sk_alloc+0x2b/0x6d0 bt_sock_alloc+0x29/0x370 iso_sock_alloc.constprop.0+0x19/0x300 iso_sock_create+0x94/0x100 Freed by task 121: kfree+0x121/0x3c0 __sk_destruct+0x42b/0x540 iso_sock_release+0x29d/0x340 __sock_release+0xa1/0x260 Check admission under the socket lock and mark the connect operation in progress before publishing its destination. Keep that flag set across route lookup and connection setup, rejecting another connect with -EBADFD before it can change the destination or attach a connection. Clear the flag after either helper returns, including on failure, so a failed setup can be retried. A separate flag is needed because the socket lock must be released before acquiring the HCI device lock, while BT_CONNECT requires an attached connection. Keep the existing state transitions and the deferred CIS completion through iso_sock_recvmsg(). Reject an existing socket attachment in __iso_chan_add() before taking a new reference or publishing either pointer, so every caller preserves the connection association. Keep the same-socket, same-connection success case for deferred CIS setup. Reject an attached socket before BIS setup so a reusable BIS is not claimed before the attachment is rejected. In CIS setup, reject a different HCI connection before iso_conn_add() and drop the per-attempt HCI hold directly. An unowned iso_conn may still carry another reference after detachment, so its destruction cannot be relied on to release that hold. iso_listen_bis() creates a fresh PA HCI/ISO pair under the device lock, so the temporary iso_conn_put() frees the ISO candidate and drops its HCI hold on rejection. iso_conn_ready() uses a freshly allocated, unpublished child with no connection, making the socket-side rejection unreachable. Fixes: ccf74f2390d6 ("Bluetooth: Add BTPROTO_ISO socket type") Cc: stable@vger.kernel.org Suggested-by: Pauli Virtanen Assisted-by: GPT-6 Astra Signed-off-by: Chengfeng Ye --- Changes in v2: - Reject an existing socket attachment in __iso_chan_add(), as suggested by Pauli Virtanen, while retaining same-connection deferred CIS setup. - Reject an attached socket before BIS setup can claim a reusable BIS. - Under the socket lock, reject a different HCI connection in CIS setup before iso_conn_add() and release the returned HCI hold directly. This also handles an unowned candidate whose iso_conn has other references. - Keep the connect admission guard to protect destination publication across route lookup and connection setup. - Rebase on the current Bluetooth fixes tree. v1: https://lore.kernel.org/r/20261004162458.3968546-1-nicoyip.dev@gmail.com Review: https://lore.kernel.org/r/225d8d84c8e5155d5af0adfbea270eeeda326021.camel@iki.fi net/bluetooth/iso.c | 47 +++++++++++++++++++++++++++++++++++---------- 1 file changed, 37 insertions(+), 10 deletions(-) diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c index 7657c2a0abbf..37e5f084d9ed 100644 --- a/net/bluetooth/iso.c +++ b/net/bluetooth/iso.c @@ -61,6 +61,7 @@ enum { BT_SK_BIG_SYNC, BT_SK_PA_SYNC, BT_SK_KILLED, + BT_SK_CONNECTING, }; struct iso_pinfo { @@ -350,6 +351,9 @@ static int __iso_chan_add(struct iso_conn *conn, struct sock *sk, return -EBUSY; } + if (iso_pi(sk)->conn) + return -EISCONN; + if (!conn->hcon) { BT_ERR("conn->hcon missing"); return -EIO; @@ -410,6 +414,11 @@ static int iso_connect_bis(struct sock *sk) hci_dev_lock(hdev); lock_sock(sk); + if (iso_pi(sk)->conn) { + err = -EISCONN; + goto unlock; + } + if (!bis_capable(hdev)) { err = -EOPNOTSUPP; goto unlock; @@ -562,6 +571,13 @@ static int iso_connect_cis(struct sock *sk) lockdep_assert_held(&hcon->hdev->lock); + /* The socket lock keeps the current attachment and its hcon stable. */ + if (iso_pi(sk)->conn && iso_pi(sk)->conn->hcon != hcon) { + hci_conn_drop(hcon); + err = -EISCONN; + goto unlock; + } + conn = iso_conn_add(hcon); if (!conn) { hci_conn_drop(hcon); @@ -1269,17 +1285,26 @@ static int iso_sock_connect(struct socket *sock, struct sockaddr_unsized *addr, addr->sa_family != AF_BLUETOOTH) return -EINVAL; - if (sk->sk_state != BT_OPEN && sk->sk_state != BT_BOUND) - return -EBADFD; + lock_sock(sk); - if (sk->sk_type != SOCK_SEQPACKET) - return -EINVAL; + if ((sk->sk_state != BT_OPEN && sk->sk_state != BT_BOUND) || + test_bit(BT_SK_CONNECTING, &iso_pi(sk)->flags)) { + err = -EBADFD; + goto done; + } + + if (sk->sk_type != SOCK_SEQPACKET) { + err = -EINVAL; + goto done; + } /* Check if the address type is of LE type */ - if (!bdaddr_type_is_le(sa->iso_bdaddr_type)) - return -EINVAL; + if (!bdaddr_type_is_le(sa->iso_bdaddr_type)) { + err = -EINVAL; + goto done; + } - lock_sock(sk); + set_bit(BT_SK_CONNECTING, &iso_pi(sk)->flags); bacpy(&iso_pi(sk)->dst, &sa->iso_bdaddr); iso_pi(sk)->dst_type = sa->iso_bdaddr_type; @@ -1291,16 +1316,18 @@ static int iso_sock_connect(struct socket *sock, struct sockaddr_unsized *addr, else err = iso_connect_bis(sk); - if (err) - return err; - lock_sock(sk); + clear_bit(BT_SK_CONNECTING, &iso_pi(sk)->flags); + if (err) + goto done; + if (!test_bit(BT_SK_DEFER_SETUP, &bt_sk(sk)->flags)) { err = bt_sock_wait_state(sk, BT_CONNECTED, sock_sndtimeo(sk, flags & O_NONBLOCK)); } +done: release_sock(sk); return err; } base-commit: 08e90633377f1b2567ab5ad6810b74c552246a07 -- 2.43.0