From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.4]) (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 2BA3248BD48; Fri, 15 May 2026 14:06:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.4 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778853999; cv=none; b=cuE0U6YjDjmLJax7yRNc7eVrmS9x3Gs8+9nQrBAcBvOmb0gDP/7CgKnrkTP4hYaKNvALssG0rSXVF/53YPRP/16+3wB3JE6KbQgat4iqjv1atW+yaxcxvm/kXx8vGQqxAaCmFAHSx+H32724U8eHs+dvKrEFoxE8E1UV+gWrxGg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778853999; c=relaxed/simple; bh=k+83qw1aBVDXTHI3o0EJipdXbePWlFTgXyIEgtF1wPE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=QbRtZ5Ab9HDYJphjipO1KLlDOydt6M+H75kImV3QHK4cAyx0xsoxLrRh4Dv7Q8CI+v3TnpQ5qDr6s/VRpUj+ZsTi5SOsbHYHsEtisIrrNsdiNuVS+8pN5JQwhoNrMAZr2S4KMXOybaStiunT1Mjz8qMIkZBBz+z0j3KdSYScafI= 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=T3c7MisN; arc=none smtp.client-ip=117.135.210.4 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="T3c7MisN" 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=En OKvtLKxGfFtXrnKl47IbY8wmgcrys1YAusjT/5P6A=; b=T3c7MisN4PwQOUSiYt M8Fxmt7OnjrKyq4S6U/L3RTD5m0YyioLrKOnkFYcCzmO6iox3tsGkbP3vqq8uMBf MhSV1R8hZ8+1JDZKmUsAapITjnf5JL7rJNLdifjpVG2gqai03hyEliUxeiwaAmlg 9XMcsTyMahQ6SXGaoCWlS4bXs= Received: from 163.com (unknown []) by gzsmtp2 (Coremail) with SMTP id PSgvCgCH1RY9KAdqHenOEg--.16120S2; Fri, 15 May 2026 22:06:01 +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 v4] Bluetooth: hci_uart: fix UAF in hci_uart_tty_close() Date: Fri, 15 May 2026 22:05:48 +0800 Message-Id: <20260515140548.393865-1-w15303746062@163.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:PSgvCgCH1RY9KAdqHenOEg--.16120S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxJw43Kr1DZFyDZF13JFWfAFb_yoWrXw1kpF ZxKF90yF4vqFWjkFyDZa1xJFyrKr4ag3y2k34fW3y5Xas8tr4jk3WIyFWIgF1UArs3Cr1S vFWDX3y5WryUZ3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07UQAw3UUUUU= X-CM-SenderInfo: jzrvjiatxuliiws6il2tof0z/xtbC-wl4XGoHKEm-FAAA31 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 tty_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 outside the HCI_UART_PROTO_READY check. 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 the hci_uart structure is freed. 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 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..333c1e1503e8 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -544,14 +544,20 @@ static void hci_uart_tty_close(struct tty_struct *tty) if (hdev) hci_uart_close(hdev); + /* + * Disable workqueues unconditionally before freeing the hu + * struct, as they might be active during the PROTO_INIT phase. + * Using disable_work_sync() instead of cancel_work_sync() + * ensures no new submissions can occur. + */ + disable_work_sync(&hu->init_ready); + disable_work_sync(&hu->write_work); + if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) { 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); - if (hdev) { if (test_bit(HCI_UART_REGISTERED, &hu->flags)) hci_unregister_dev(hdev); -- 2.34.1