From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 606B8284690; Sat, 30 May 2026 18:15:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164933; cv=none; b=OhuQlrb5YPgZGGAAhiJljoux1vqhkw26CxrtNKA2NimiX/jm3mTAlc3YtYZzHF2SkL0zRJH11EOvqRtsWEKGPzncp56yRIUgczkD/ESU+xEbFzR8JfCvaRHi3/XBpwR05pgZCDeXW5VgnLJlzP73oR5z88A7V4fTK7I26nHNrlA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780164933; c=relaxed/simple; bh=RXpiqktoqUcT36vHbQGlUUmkbSs3NqJfocYTjr1EIXA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FnNmqjw03Zkb/PxDKyysTM/8cdUKEBvs4MD2vxLHi1nq8c0OzQAySH9fn0QdSTUO4xsCTLbIgPBnyfGnJdOR+9jldLM6JUW4vAUdaDVdm84DJHwERvHMtWpyOQSoYGnZO1d9RKbRRB34R2voyKhUPpbdMezx0dxs9BSSoyArgNc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UBZX4y9N; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="UBZX4y9N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A46AD1F00893; Sat, 30 May 2026 18:15:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780164932; bh=Ev6D3rrs7zu8hUmPQpbMlzL0qqCPRhhQGZvDAF3ix1s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UBZX4y9NiY734x22+baXQHsg5oIHZ3m3e8019FzXMjZmaj3qLb2vuYPm520JMDt7c kF3RVwlAb4aoqrYVMmcQQSfYGs+mEpTlQe8aGGLnSFuoOs6p0AMq0CY5RO5DamOyRR ildBdCpCSJWggT9LdPowFDd2+gXmLuQozMHscMwk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mingyu Wang <25181214217@stu.xidian.edu.cn>, Luiz Augusto von Dentz Subject: [PATCH 5.15 684/776] Bluetooth: hci_uart: fix UAFs and race conditions in close and init paths Date: Sat, 30 May 2026 18:06:38 +0200 Message-ID: <20260530160257.539810671@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160240.228940103@linuxfoundation.org> References: <20260530160240.228940103@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mingyu Wang <25181214217@stu.xidian.edu.cn> commit c1bb9336ae6b54a5f6a353c4bd4ed9a4307e429b upstream. Vulnerabilities leading to Use-After-Free (UAF) and Null Pointer Dereference (NPD) conditions were observed in the lifecycle management of hci_uart. The primary issue arises because the workqueues (init_ready and write_work) are only flushed/cancelled if the HCI_UART_PROTO_READY flag is set during TTY close. If a hangup occurs before setup completes, hci_uart_tty_close() skips the teardown of these workqueues and proceeds to free the `hu` struct. When the scheduled work executes later, it blindly dereferences the freed `hu` struct. Furthermore, several data races and UAFs were identified in the teardown sequence: 1. Calling hci_uart_flush() from hci_uart_close() without effectively disabling write_work causes a race condition where both can concurrently double-free hu->tx_skb. This happens because protocol timers can concurrently invoke hci_uart_tx_wakeup() and requeue write_work. 2. Calling hci_free_dev(hdev) before hu->proto->close(hu) causes a UAF when vendor specific protocol close callbacks dereference hu->hdev. 3. In the initialization error paths, failing to take the proto_lock write lock before clearing PROTO_READY leads to races with active readers. Additionally, hci_uart_tty_receive() accesses hu->hdev outside the read lock, leading to UAFs if the initialization error path frees hdev concurrently. Fix these synchronization and lifecycle issues by: 1. Re-ordering hci_uart_tty_close() to clear HCI_UART_PROTO_READY first, followed immediately by a cancel_work_sync(&hu->write_work). Clearing the flag locks out concurrent protocol timers from successfully invoking hci_uart_tx_wakeup(), effectively rendering the cancellation permanent and preventing the tx_skb double-free. 2. Note: Clearing PROTO_READY early causes hci_uart_close() to skip hu->proto->flush(). This is perfectly safe in the tty_close path because hu->proto->close() executes shortly after, which intrinsically purges all protocol SKB queues and tears down the state. 3. Relocating hu->proto->close(hu) strictly prior to hci_free_dev(hdev) across all close and error paths to prevent vendor-level UAFs. 4. Moving the hdev->stat.byte_rx increment in hci_uart_tty_receive() inside the proto_lock read-side critical section to safely synchronize with device unregistration. 5. Adding cancel_work_sync(&hu->write_work) to hci_uart_close() to safely flush the workqueue before hci_uart_flush() is invoked via the HCI core. 6. Utilizing cancel_work_sync() instead of disable_work_sync() across all paths to prevent permanently breaking user-space retry capabilities. Fixes: 3b799254cf6f ("Bluetooth: hci_uart: Cancel init work before unregistering") Cc: stable@vger.kernel.org Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn> Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman --- drivers/bluetooth/hci_ldisc.c | 48 +++++++++++++++++++++++++++++++++++------- 1 file changed, 40 insertions(+), 8 deletions(-) --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -194,7 +194,15 @@ void hci_uart_init_work(struct work_stru err = hci_register_dev(hu->hdev); if (err < 0) { BT_ERR("Can't register HCI device"); + + percpu_down_write(&hu->proto_lock); clear_bit(HCI_UART_PROTO_READY, &hu->flags); + percpu_up_write(&hu->proto_lock); + + /* Safely cancel work after clearing flags */ + cancel_work_sync(&hu->write_work); + + /* Close protocol before freeing hdev */ hu->proto->close(hu); hdev = hu->hdev; hu->hdev = NULL; @@ -263,8 +271,12 @@ static int hci_uart_open(struct hci_dev /* Close device */ static int hci_uart_close(struct hci_dev *hdev) { + struct hci_uart *hu = hci_get_drvdata(hdev); + BT_DBG("hdev %p", hdev); + cancel_work_sync(&hu->write_work); + hci_uart_flush(hdev); hdev->flush = NULL; return 0; @@ -525,6 +537,7 @@ static void hci_uart_tty_close(struct tt { struct hci_uart *hu = tty->disc_data; struct hci_dev *hdev; + bool proto_ready; BT_DBG("tty %p", tty); @@ -534,24 +547,38 @@ static void hci_uart_tty_close(struct tt if (!hu) return; - hdev = hu->hdev; - if (hdev) - hci_uart_close(hdev); + /* Wait for init_ready to finish to prevent registration races */ + cancel_work_sync(&hu->init_ready); - if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) { + proto_ready = test_bit(HCI_UART_PROTO_READY, &hu->flags); + if (proto_ready) { percpu_down_write(&hu->proto_lock); clear_bit(HCI_UART_PROTO_READY, &hu->flags); percpu_up_write(&hu->proto_lock); + } - cancel_work_sync(&hu->init_ready); - cancel_work_sync(&hu->write_work); + /* + * Unconditionally cancel write_work AFTER clearing PROTO_READY. + * This ensures that concurrent protocol timers cannot requeue + * write_work via hci_uart_tx_wakeup(), permanently preventing + * double-free races and UAFs. + */ + cancel_work_sync(&hu->write_work); + + hdev = hu->hdev; + if (hdev) + hci_uart_close(hdev); /* proto->flush is safely skipped */ + if (proto_ready) { if (hdev) { if (test_bit(HCI_UART_REGISTERED, &hu->flags)) hci_unregister_dev(hdev); - hci_free_dev(hdev); } + /* Close protocol before freeing hdev (intrinsically purges queues) */ hu->proto->close(hu); + + if (hdev) + hci_free_dev(hdev); } clear_bit(HCI_UART_PROTO_SET, &hu->flags); @@ -619,11 +646,12 @@ static void hci_uart_tty_receive(struct * tty caller */ hu->proto->recv(hu, data, count); - percpu_up_read(&hu->proto_lock); if (hu->hdev) hu->hdev->stat.byte_rx += count; + percpu_up_read(&hu->proto_lock); + tty_unthrottle(tty); } @@ -694,6 +722,10 @@ static int hci_uart_register_dev(struct percpu_down_write(&hu->proto_lock); clear_bit(HCI_UART_PROTO_INIT, &hu->flags); percpu_up_write(&hu->proto_lock); + /* Cancel work after clearing flags */ + cancel_work_sync(&hu->write_work); + + /* Close protocol before freeing hdev */ hu->proto->close(hu); hu->hdev = NULL; hci_free_dev(hdev);