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 5E68C4E36C0; Tue, 13 Oct 2026 12:46:07 +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=1791895568; cv=none; b=ilHbh2G0yW37677e8j5+0zntVmSV0cycUTao/d2LttnB+ok+xRIuW73u0gaBwAfp5YHooEoXHmdslEKqul3H4PMziaOKz8JsCigWdClUUlun/rghpzfLw/ZNzEjeMbl9WmoNGeFQGAE/bLiQSvdnXvHNjFte12ZoBVFwLAP72vk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791895568; c=relaxed/simple; bh=G+Kv+FryJQ4sD6ZqmFnVt7jcGsH8pFOhAjzoqYXykNI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HLaOvm8JnM5k32TFvPnG31MrlD9HDiSG9SJvybryKy1iORCJWq7+bwjHOKTdVOGyldB8BhXxTMA9GA9diw7B7Pa4zilXturouGLQGA5E/0povkJMQk6KEOtaY2kE511kvcy5PvuuKMQ7LlqTaE7ZKT/inszk7KfraWslEQFjD/A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=aVF9HDY8; 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="aVF9HDY8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA9EF1F000FF; Tue, 13 Oct 2026 12:46:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791895567; bh=7cX8KHTPA1/6GDYYj62QZNdR3BoXopYChbrEeHWrsak=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aVF9HDY88NMZwIAGHReMUOPqhHI0EpEmf+vrkcpZBmN/lB2nF6M6mznt8LBCZWSsI 7k8u3CiUUsHiPuXhfkoAxahwBrnNU1mwPn4XEJjwNfzharfsG8k3PCtLeSYISTYVnV c2SvKlB7dIhQmup30pf+bK5COKD9NlhGZiV4bkUM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+5fabc1ae99ff40690d84@syzkaller.appspotmail.com, Johan Hovold , Sasha Levin , stable@kernel.org Subject: [PATCH 6.12 316/497] tty: port: fix tty_port_tty_vhangup() race Date: Tue, 13 Oct 2026 13:38:03 +0200 Message-ID: <20261013112915.401974650@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112907.864180619@linuxfoundation.org> References: <20261013112907.864180619@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold [ Upstream commit b48820de8c1a596c5b99775524dfce73c6576c5d ] Drivers rely on tty_port_tty_vhangup() to synchronously hang up their ports before tearing down resources as part of deregistration (e.g. on physical disconnect). If tty_port_tty_vhangup() races with another hangup it may however return before the port has been shut down. This is in turn can lead to use-after-free and NULL-pointer dereferences in racing ioctls (including a synchronous hangup) and in processing of racing asynchronous hangups (carrier loss). Add the missing serialisation to tty_port_tty_vhangup() and tty_port_hangup() so that the former does not return until the port has been shut down also when there is a racing hangup. Note that serial core does not use tty_port_hangup(), but it already holds the port mutex when clearing port->tty and shutting down the port in uart_hangup(). Fixes: 7ca0ff9ab321 ("tty: Add a full port_close function") Cc: stable@kernel.org # 2.6.32: 2b5eac0f8c6e: tty: introduce and use tty_port_tty_vhangup() helper Cc: stable@kernel.org # 2.6.32 Reported-by: syzbot+5fabc1ae99ff40690d84@syzkaller.appspotmail.com Link: https://lore.kernel.org/6a944641.4d659fcc.734b4.003c.GAE@google.com Signed-off-by: Johan Hovold Link: https://patch.msgid.link/20260910125114.640880-1-johan@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/tty_port.c | 87 ++++++++++++++++++++++++++-------------- include/linux/tty_port.h | 22 +--------- 2 files changed, 60 insertions(+), 49 deletions(-) diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c index 10d707e3c0344..9a1bcea3597ac 100644 --- a/drivers/tty/tty_port.c +++ b/drivers/tty/tty_port.c @@ -339,19 +339,9 @@ void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty) } EXPORT_SYMBOL(tty_port_tty_set); -/** - * tty_port_shutdown - internal helper to shutdown the device - * @port: tty port to be shut down - * @tty: the associated tty - * - * It is used by tty_port_hangup() and tty_port_close(). Its task is to - * shutdown the device if it was initialized (note consoles remain - * functioning). It lowers DTR/RTS (if @tty has HUPCL set) and invokes - * @port->ops->shutdown(). - */ -static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty) +static void tty_port_shutdown_locked(struct tty_port *port, struct tty_struct *tty) { - guard(mutex)(&port->mutex); + lockdep_assert_held(&port->mutex); if (port->console) return; @@ -371,6 +361,23 @@ static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty) port->ops->shutdown(port); } +/** + * tty_port_shutdown - internal helper to shutdown the device + * @port: tty port to be shut down + * @tty: the associated tty + * + * It is used by tty_port_hangup() and tty_port_close(). Its task is to + * shutdown the device if it was initialized (note consoles remain + * functioning). It lowers DTR/RTS (if @tty has HUPCL set) and invokes + * @port->ops->shutdown(). + */ +static void tty_port_shutdown(struct tty_port *port, struct tty_struct *tty) +{ + guard(mutex)(&port->mutex); + + tty_port_shutdown_locked(port, tty); +} + /** * tty_port_hangup - hangup helper * @port: tty port @@ -384,36 +391,58 @@ void tty_port_hangup(struct tty_port *port) { struct tty_struct *tty; - scoped_guard(spinlock_irqsave, &port->lock) { - port->count = 0; - tty = port->tty; - if (tty) - set_bit(TTY_IO_ERROR, &tty->flags); - port->tty = NULL; - } + scoped_guard(mutex, &port->mutex) { + scoped_guard(spinlock_irqsave, &port->lock) { + port->count = 0; + tty = port->tty; + if (tty) + set_bit(TTY_IO_ERROR, &tty->flags); + port->tty = NULL; + } - tty_port_set_active(port, false); - tty_port_shutdown(port, tty); + tty_port_set_active(port, false); + tty_port_shutdown_locked(port, tty); + } tty_kref_put(tty); wake_up_interruptible(&port->open_wait); wake_up_interruptible(&port->delta_msr_wait); } EXPORT_SYMBOL(tty_port_hangup); -void __tty_port_tty_hangup(struct tty_port *port, bool check_clocal, bool async) +/** + * tty_port_tty_hangup - helper to hang up a tty asynchronously + * @port: tty port + * @check_clocal: hang only ttys with %CLOCAL unset? + */ +void tty_port_tty_hangup(struct tty_port *port, bool check_clocal) { scoped_guard(tty_port_tty, port) { struct tty_struct *tty = scoped_tty(); - if (!check_clocal || !C_CLOCAL(tty)) { - if (async) - tty_hangup(tty); - else - tty_vhangup(tty); - } + if (!check_clocal || !C_CLOCAL(tty)) + tty_hangup(tty); + } +} +EXPORT_SYMBOL_GPL(tty_port_tty_hangup); + +/** + * tty_port_tty_vhangup - helper to hang up a tty synchronously + * @port: tty port + */ +void tty_port_tty_vhangup(struct tty_port *port) +{ + struct tty_struct *tty; + + mutex_lock(&port->mutex); + tty = tty_port_tty_get(port); + mutex_unlock(&port->mutex); + + if (tty) { + tty_vhangup(tty); + tty_kref_put(tty); } } -EXPORT_SYMBOL_GPL(__tty_port_tty_hangup); +EXPORT_SYMBOL_GPL(tty_port_tty_vhangup); /** * tty_port_tty_wakeup - helper to wake up a tty diff --git a/include/linux/tty_port.h b/include/linux/tty_port.h index 5e2cd738aceaf..7d4e7789e6cbb 100644 --- a/include/linux/tty_port.h +++ b/include/linux/tty_port.h @@ -235,7 +235,8 @@ bool tty_port_carrier_raised(struct tty_port *port); void tty_port_raise_dtr_rts(struct tty_port *port); void tty_port_lower_dtr_rts(struct tty_port *port); void tty_port_hangup(struct tty_port *port); -void __tty_port_tty_hangup(struct tty_port *port, bool check_clocal, bool async); +void tty_port_tty_hangup(struct tty_port *port, bool check_clocal); +void tty_port_tty_vhangup(struct tty_port *port); void tty_port_tty_wakeup(struct tty_port *port); int tty_port_block_til_ready(struct tty_port *port, struct tty_struct *tty, struct file *filp); @@ -254,25 +255,6 @@ static inline int tty_port_users(struct tty_port *port) return port->count + port->blocked_open; } -/** - * tty_port_tty_hangup - helper to hang up a tty asynchronously - * @port: tty port - * @check_clocal: hang only ttys with %CLOCAL unset? - */ -static inline void tty_port_tty_hangup(struct tty_port *port, bool check_clocal) -{ - __tty_port_tty_hangup(port, check_clocal, true); -} - -/** - * tty_port_tty_vhangup - helper to hang up a tty synchronously - * @port: tty port - */ -static inline void tty_port_tty_vhangup(struct tty_port *port) -{ - __tty_port_tty_hangup(port, false, false); -} - #ifdef CONFIG_TTY void tty_kref_put(struct tty_struct *tty); __DEFINE_CLASS_IS_CONDITIONAL(tty_port_tty, true); -- 2.53.0