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 DCFEE3B14A9; Sat, 17 Oct 2026 17:03:06 +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=1792256587; cv=none; b=J2ABIo7aO6ss/IZm2iSCZbx4U9HhiSZ6DEfqaOGr+afI1f3ovpV3wlUSoZGazBaZWF5v1gZshpfJjXX8S71fUuY/APsr4S/XvMPKzylloUTt5qA4G2r0cQtkybPkfmu9ZxqQz5IlwfVd/+sVWAISFihe6jvoWrMXTFADK5/aOBg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792256587; c=relaxed/simple; bh=MkDdSYtqA8HHrVvPBko4RP78LTvWqhVUOwzg1+qLRoc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Tb5O7jbwNs0qFyJocZ0gRm4z6HbeuOj0pMAULVsYFRCZdHsUXIqP+2Kiudg3ahzzfz9N4LL+lrphALbsJW/x7CYdnzxMwI1EKzZPVlldBMbZ8u/UO6hfQ7DV3fkGEpnk+3k1XDQVpZW+XeJRpyZoYhZrZfkuTYCFU6uE5NVRacU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qXpBxRXh; 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="qXpBxRXh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 328941F000C4; Sat, 17 Oct 2026 17:03:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792256586; bh=QkhgyHU0KhHofy4liTmkjNX+jJkFOhowj9dcDGT+kZM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qXpBxRXhgp81gv1tj4PO+E9PbarsmrXuHQcK/cCejzKm7UwlY3x7kMs5IO4G6X71k h2G+mANjqKD8K1WpQGeFaJt3uOpdRvLkiujNmkqvnta9LkYZl+YSrBwWPP6Bcgojjc itiO17x3O82+VoECL+Rpy0DIGxeoHZ2YCHTtpwEw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Johan Hovold Subject: [PATCH 6.6 0284/1674] tty: abort break signalling on hangup Date: Sat, 17 Oct 2026 17:42:36 +0200 Message-ID: <20261017160438.404892795@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160431.119607952@linuxfoundation.org> References: <20261017160431.119607952@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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold commit 845a2737e0f5ffe5ca8d38de556012b0c9472cdd upstream. The break ioctls can race with hangup and end up calling into a tty driver for a device that is already gone or powered down. Drivers must handle this race, but TCSBRK and TCSBRKP should still be aborted to avoid calling back into the driver after a user-controlled timeout (possibly even after the tty has been reopened). Note that drivers should disable any break state on shutdown so just return on hangup (calling break_ctl() again is racy and will most likely fail for drivers handling the race). Fixes: f34d7a5b7010 ("tty: The big operations rework") Cc: stable Signed-off-by: Johan Hovold Link: https://patch.msgid.link/20260903163736.1499280-1-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 36 +++++++++++++++++++++++++++--------- include/linux/tty.h | 1 + 2 files changed, 28 insertions(+), 9 deletions(-) --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -629,6 +629,8 @@ static void __tty_hangup(struct tty_stru tty_ldisc_hangup(tty, cons_filp != NULL); + wake_up_interruptible(&tty->break_wait); + spin_lock_irq(&tty->ctrl.lock); clear_bit(TTY_THROTTLED, &tty->flags); clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); @@ -2460,6 +2462,7 @@ static int tiocgetd(struct tty_struct *t * send_break - performed time break * @tty: device to break on * @duration: timeout in mS + * @file: file object * * Perform a timed break on hardware that lacks its own driver level timed * break functionality. @@ -2467,8 +2470,9 @@ static int tiocgetd(struct tty_struct *t * Locking: * @tty->atomic_write_lock serializes */ -static int send_break(struct tty_struct *tty, unsigned int duration) +static int send_break(struct file *file, struct tty_struct *tty, unsigned int duration) { + long timeout; int retval; if (tty->ops->break_ctl == NULL) @@ -2482,13 +2486,26 @@ static int send_break(struct tty_struct return -EINTR; retval = tty->ops->break_ctl(tty, -1); - if (!retval) { - msleep_interruptible(duration); - retval = tty->ops->break_ctl(tty, 0); - } else if (retval == -EOPNOTSUPP) { - /* some drivers can tell only dynamically */ - retval = 0; + if (retval) { + if (retval == -EOPNOTSUPP) { + /* some drivers can tell only dynamically */ + retval = 0; + } + goto out_unlock; + } + + timeout = msecs_to_jiffies(duration); + timeout = wait_event_interruptible_timeout(tty->break_wait, + tty_hung_up_p(file), + timeout); + /* return early on hangup only */ + if (timeout > 0) { + retval = -EIO; + goto out_unlock; } + + retval = tty->ops->break_ctl(tty, 0); +out_unlock: tty_write_unlock(tty); if (signal_pending(current)) @@ -2741,10 +2758,10 @@ long tty_ioctl(struct file *file, unsign * This is used by the tcdrain() termios function. */ if (!arg) - return send_break(tty, 250); + return send_break(file, tty, 250); return 0; case TCSBRKP: /* support for POSIX tcsendbreak() */ - return send_break(tty, arg ? arg*100 : 250); + return send_break(file, tty, arg ? arg * 100 : 250); case TIOCMGET: return tty_tiocmget(tty, p); @@ -3107,6 +3124,7 @@ struct tty_struct *alloc_tty_struct(stru init_ldsem(&tty->ldisc_sem); init_waitqueue_head(&tty->write_wait); init_waitqueue_head(&tty->read_wait); + init_waitqueue_head(&tty->break_wait); INIT_WORK(&tty->hangup_work, do_tty_hangup); mutex_init(&tty->atomic_write_lock); spin_lock_init(&tty->ctrl.lock); --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -237,6 +237,7 @@ struct tty_struct { struct fasync_struct *fasync; wait_queue_head_t write_wait; wait_queue_head_t read_wait; + wait_queue_head_t break_wait; struct work_struct hangup_work; void *disc_data; void *driver_data;