From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.5]) (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 4E3033016EE; Thu, 14 May 2026 15:18:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778771890; cv=none; b=cmaf/iSSMDCoaHRZnKDIuj0TaxaCMDPSICez5OSv3bony/6lyqGoph2n6YKMNNYA75aQDGF51EqTdqLOQukn5BgmKonn45ZLlOkmaW6v9OnSapHr6o70RPD9gi7rgvwGT/0CfUWd8pit3Ts0MTZIS3/RjtpgppVhzg/Efho63GI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778771890; c=relaxed/simple; bh=8XUG37OWN4efwu3q/z9ggIvSSNC4KX/6ialqwt4WdrI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=dKwCeZNOJGHII3vkMhoWc7WNV5zlXgMWRJEP/o9CEERbZIgo9UvrVXaz7Xbmr/iWkg4LqIeH1MP25LimIE1+s7uycsUb6N8Wsgp7eBdT0jX+OdvxXwk5DxxKH/R4fyyXVNi/hvqY5u1KiDaHEJ6Sr+bol2MUhBMy/k5MA41CYRQ= 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=NWIaxTCP; arc=none smtp.client-ip=220.197.31.5 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="NWIaxTCP" 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=8H uNF7ABAjpQi3quTa2io9ZNZfMjbhtTu7LU/iNR8f8=; b=NWIaxTCPTO4CyhYDs9 yw+wXrOjamQ+aQWIIfpZQo4CVgQKP5tLciZdQzj44FtQZnuab7b6ZzeJKaZaYmcG whwyP1pvA1auQinjghrkag2hQ5UQ/z54fI4hUki8bl58nmG2s7auQ5+tWwz1Vxym f8sNdrBRra7sauNJbf+JCK5Cc= Received: from 163.com (unknown []) by gzga-smtp-mtada-g1-1 (Coremail) with SMTP id _____wD3PxaD5wVqQ_dZBQ--.35881S2; Thu, 14 May 2026 23:17:34 +0800 (CST) From: To: pmenzel@molgen.mpg.de, marcel@holtmann.org, luiz.dentz@gmail.com, linux-bluetooth@vger.kernel.org Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Mingyu Wang <25181214217@stu.xidian.edu.cn> Subject: [PATCH v2] Bluetooth: hci_uart: fix UAF in hci_uart_tty_close() Date: Thu, 14 May 2026 23:17:22 +0800 Message-Id: <20260514151722.382161-1-w15303746062@163.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <505b56bd-e5fd-4feb-a6e3-1d8269609277@molgen.mpg.de> References: <505b56bd-e5fd-4feb-a6e3-1d8269609277@molgen.mpg.de> 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:_____wD3PxaD5wVqQ_dZBQ--.35881S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxJw43Kr1DZFyDZF13JFWfAFb_yoWrJr1kpF s3KF98AFWktrWDKF1qva1xAFyrKrn2gFW2k34fX3y5Z3W5tr4vk3WIkayIgF1UCrs3Cr4S vF4UXay5W3WUZw7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07UGsj8UUUUU= X-CM-SenderInfo: jzrvjiatxuliiws6il2tof0z/xtbC5A743GoF544J0AAA3R 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 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 cancel_work_sync() calls and proceeds to free the `hu` struct. When the delayed workqueue executes, it blindly dereferences the freed `hu` struct. Fix this by moving the cancel_work_sync() calls outside the HCI_UART_PROTO_READY check, ensuring that any pending works are unconditionally cancelled 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 cancel_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") Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn> --- Changes in v2: - Added KASAN/ODEBUG crash trace. - Added explanation for the absence of a standalone reproducer (highly timing-dependent race condition). - Added Fixes tag pointing to commit 3b799254cf6f. drivers/bluetooth/hci_ldisc.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c index 275ea865bc29..566e1c525ee2 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -544,14 +544,18 @@ static void hci_uart_tty_close(struct tty_struct *tty) if (hdev) hci_uart_close(hdev); + /* + * Always cancel workqueues unconditionally before freeing the hu + * struct, as they might be active during the PROTO_INIT phase. + */ + cancel_work_sync(&hu->init_ready); + cancel_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