From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.3]) (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 30FC91CFBA; Sat, 16 May 2026 02:22:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.3 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778898181; cv=none; b=HOFic4CY3oROxgAQY99DTabEvkQtJE2H78/ypnVnhlxK3peBTpf3AcP1vZdXSrJ+G76y7Opns9/pO+whxR0JrSpW/f9X+85F2HQpOl+nKeXE7o2VsfJCzubqQK0Kg9xg/UdXc16Z6m4+V0H5EkoNC8vYToKjxggRqgZR3kzfusw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778898181; c=relaxed/simple; bh=vZ8HI72OFbthSBJEsoHa2z/u4GgfSwQeyQsy/GOGEXY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=eGU6PITCWrRKWL4GtwBptUzrSHInGdFTqCH1EtZm+YzGweOoFlysq4qgPj37jSpmr/okzk0YomWpG+napEKbee99y0PDyxx5t6EpSQAbaK7tcBXWSfixqmwE+EBsoIJBnRg62US9Y3MqwBgUBaRGRCAA5YASq3zRIUt5cAZxBRg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=VrQQQOYT; arc=none smtp.client-ip=220.197.31.3 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="VrQQQOYT" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=o8 Z/FOlH+CBwFDIxdt/BJ/uYRlERnR/Hp8g+li8D4z8=; b=VrQQQOYT2D/sBVieqQ 5pYNcoA55AtWkEPn68KYtgm8wdwfO4PM6fXWrf71YE/mGq+6FZxr7Obxp2CpUhp4 v5Ir34BEG+ZL37zKwJ8ypgYSpfZ5Ucqqe28+zlRk5JYKka9qqr6XX94KnPLmjXyQ lA55Z0kqYUhwNn8gIxheNc3P4= Received: from 163.com (unknown []) by gzsmtp3 (Coremail) with SMTP id PigvCgD3Vy_K1Adq3dBFDg--.212S2; Sat, 16 May 2026 10:22:15 +0800 (CST) From: To: luiz.dentz@gmail.com, pmenzel@molgen.mpg.de, marcel@holtmann.org, linux-bluetooth@vger.kernel.org Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, greg@kroah.com, stable@vger.kernel.org, Mingyu Wang <25181214217@stu.xidian.edu.cn> Subject: [PATCH v5] Bluetooth: hci_uart: fix UAF in hci_uart_tty_close() Date: Sat, 16 May 2026 10:22:00 +0800 Message-Id: <20260516022200.396369-1-w15303746062@163.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:PigvCgD3Vy_K1Adq3dBFDg--.212S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxJw43Kr1DZFyDZF13JFWfAFb_yoWrCw18pF 9xKF90ya1DJFWjkFyDZa1xAFyrKFs2g3y2y34fW3y5Xwn8tr1jy3WIyFWI93WUAr95Cr1S vFWqq3y5WFyUZ3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07UlQ6XUUUUU= X-CM-SenderInfo: jzrvjiatxuliiws6il2tof0z/xtbC-xfGqmoH1NcPIQAA3E From: Mingyu Wang <25181214217@stu.xidian.edu.cn> A Use-After-Free (UAF) vulnerability and a subsequent kernel panic were observed in hci_uart_write_work() due to a race condition between the initialization of the HCI UART line discipline and concurrent TTY hangup. This issue was triggered by our custom device emulation and fuzzing framework (DevGen) on the v6.18 kernel. Due to the highly timing-dependent nature of this race condition (requiring a precise interleaving of TIOCVHANGUP and protocol setup), Syzkaller failed to extract a reliable standalone C reproducer (reproducer is too unreliable: 0.00). The crash trace is as follows: ODEBUG: free active (active state 0) object: ffff88804024e870 object type: work_struct hint: hci_uart_write_work+0x0/0x940 WARNING: CPU: 0 PID: 338273 at lib/debugobjects.c:612 debug_print_object+0x1a2/0x2b0 ... Call Trace: debug_check_no_obj_freed+0x3ec/0x520 kfree+0x3f0/0x6c0 hci_uart_tty_close+0x127/0x2a0 k_ldisc_close+0x113/0x1a0 tty_ldisc_kill+0x8e/0x150 tty_ldisc_hangup+0x3c1/0x730 __tty_hangup.part.0+0x3fd/0x8a0 tty_ioctl+0x120f/0x1690 __x64_sys_ioctl+0x18f/0x210 do_syscall_64+0xcb/0xfa0 entry_SYSCALL_64_after_hwframe+0x77/0x7f The issue arises because the workqueues (init_ready and write_work) are only flushed/cancelled if the HCI_UART_PROTO_READY flag is set. However, during the protocol initialization phase (HCI_UART_PROTO_INIT), the underlying protocol may schedule work. If a hangup occurs before the setup completes and the READY flag is set, 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. Fix this by moving the workqueue teardown to the very beginning of hci_uart_tty_close(), outside the HCI_UART_PROTO_READY check and prior to calling hci_uart_close(). Furthermore, use disable_work_sync() instead of cancel_work_sync() to unconditionally disable the works. This ensures that any pending works are cancelled and no new submissions can occur before or during the teardown of the device connection. Note that hu->init_ready and hu->write_work are initialized in hci_uart_tty_open(), so it is always safe to call disable_work_sync() on them in hci_uart_tty_close(), even if the protocol was never fully attached. 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> --- Changes in v5: - Moved disable_work_sync() to the very top of hci_uart_tty_close(), before hci_uart_close(), to prevent any concurrent re-queuing during device shutdown and resolve Sashiko static analysis warnings. Changes in v4: - Adopted Luiz's suggestion to use disable_work_sync() instead of cancel_work_sync() to prevent new work submissions during teardown. Changes in v3: - Added 'Cc: stable' tag as requested by the stable bot. Changes in v2: - Added KASAN/ODEBUG crash trace. drivers/bluetooth/hci_ldisc.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c index 275ea865bc29..ebdbcd567cd2 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -540,6 +540,15 @@ static void hci_uart_tty_close(struct tty_struct *tty) if (!hu) return; + /* + * Disable workqueues unconditionally before tearing down the + * connection, as they might be active during the PROTO_INIT phase. + * Using disable_work_sync() ensures no new submissions can occur + * during or after hci_uart_close(). + */ + disable_work_sync(&hu->init_ready); + disable_work_sync(&hu->write_work); + hdev = hu->hdev; if (hdev) hci_uart_close(hdev); @@ -549,9 +558,6 @@ static void hci_uart_tty_close(struct tty_struct *tty) 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); - if (hdev) { if (test_bit(HCI_UART_REGISTERED, &hu->flags)) hci_unregister_dev(hdev); -- 2.34.1