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 E31B44E0201 for ; Mon, 5 Oct 2026 20:16:40 +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=1791231402; cv=none; b=QdlcyGLVKjcEaKchBWYwwLjFA+Df2xUg1ZSicH1LXwXcVGHuEpZulWWo+LDordoS8PPVCB8hb+ea8wkmRT2smWafZsKEvg0Y+2scwYC04NbpOG4wJbbOsuxxDZ7pWRI5R5xkDUZ1+nFlRWVMbivE0pT/kXb5YBJzVxwELt+q0+U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791231402; c=relaxed/simple; bh=dC7SxuZKh17BNT2uOpuctHpedjBDGmGXuzMUN6RuMzQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mlaIfT0k3TJt2aDGzedecSaY+NcrRANbFy7MjPcTnGZykdX0aTYqnOKCbTw0z+sQ+Dk0n271zVGrgRY6MFCp//nYH7FxHTpJ9ssDK9Cuzxb3k5uCLEft8kx9Vpob+i9cp211Vui8c99mYsBJUF7qTsy/M/mQmnUZeaMkQsjYYxw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P2J7ky/W; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="P2J7ky/W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 590F71F00898; Mon, 5 Oct 2026 20:16:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791231400; bh=sQBdCc5ZNebt6sdsjeOd4kIKgzKRTtpPHLOTsQjIVpg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=P2J7ky/Wrjxpnp3aM5Kx2cDGFtRiy7gML6igNNIvRBGPvQib8WF+PzHRIJAmeiwAV 8mX49YBV6dN5Wmuvb85SByWo6Gp62osSUJKEwU0wrr3DnaIO3D4vYXGZzYbZfdKaoA Ud3RJbiazeDBmTFVuM6474kEJxPoOvwBt7v3URgQn8EQiwPF635x119fVy4TcY+YVM S42rt2RNg0USLF/gp6ic+eI+eGpUziPViPJoAkv5FNWaLNzuyz2/hvBjOqTtWgp+zb iQESOiksPa9GXTQ0994rkPEOCrv8P/5uQYw4rLyNjxWxbhdtS8/Pc/NCjs7yZGyTQj 2/efq+V11fWDw== From: Sasha Levin To: stable@vger.kernel.org Cc: Johan Hovold , stable , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH 5.15.y 2/2] tty: abort break signalling on hangup Date: Mon, 5 Oct 2026 16:16:35 -0400 Message-ID: <20261005201512.3067187-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261005201512.3067187-1-sashal@kernel.org> References: <2026100529-visitor-zoning-adb2@gregkh> <20261005201512.3067187-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Johan Hovold [ Upstream commit 845a2737e0f5ffe5ca8d38de556012b0c9472cdd ] 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 Signed-off-by: Sasha Levin --- drivers/tty/tty_io.c | 36 +++++++++++++++++++++++++++--------- include/linux/tty.h | 1 + 2 files changed, 28 insertions(+), 9 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index c92416df20d6e..d672b17aaff98 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -636,6 +636,8 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session) 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); @@ -2459,6 +2461,7 @@ static int tiocgetd(struct tty_struct *tty, int __user *p) * 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. @@ -2466,8 +2469,9 @@ static int tiocgetd(struct tty_struct *tty, int __user *p) * 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) @@ -2481,13 +2485,26 @@ static int send_break(struct tty_struct *tty, unsigned int duration) 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)) @@ -2740,10 +2757,10 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg) * 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); @@ -3112,6 +3129,7 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx) 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); diff --git a/include/linux/tty.h b/include/linux/tty.h index 168e57e40bbb8..9501a8640baa8 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -188,6 +188,7 @@ 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; -- 2.53.0