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 E722C37F322 for ; Mon, 5 Oct 2026 08:50:52 +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=1791190254; cv=none; b=Db5TB2huUnuA8Exhsq3kNpB11qL2LTJF3gx5oFX2d6vfo0BCHvyZ3DZ1/6HBMN25UtEJZ3riuqqdh4VfdEKdrUwFfbN2TOvpRDYKDMJDM+KWdaJCUBgy47+M1qp2TfvirZpbfzRmVXu7yFjJMJWHHR9tZMIFxlnLtC/KNXgUW6w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791190254; c=relaxed/simple; bh=b8/YhC7hoq5Aso6C3RM8aqMXNHLtIHgYK/rglcsWEhc=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=O6qmFPFAqbGC1nqV6g6KoVCRJMjHoByqXYkM/UEl6BKlR7Bz05xwDQVkSJfTx9MhJiOALvbHAajGFmsdTKbSbWXtbltUOmUGSbZKe+RgdxXA3js38jvq8p40qLqh0AQFu7M/5H7VRY3DNfPjgy4B0/N6UuH4WM56eHdN1oDAR1o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=l/E8BIql; 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="l/E8BIql" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 497FC1F000FF; Mon, 5 Oct 2026 08:50:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791190252; bh=T3hsdVGPyXWgDP4jK2E5IK2dhlzKwxKbfesbJMnmC9M=; h=Subject:To:Cc:From:Date; b=l/E8BIqlJjM7EkZ3GAQE3W6eKqCEC2Wdm3WoHavvBDQBWxLwNGOko/vAICg9pk87v FA6X6d8UBzYJ4JIUOqYxiMsiHoVf5EopkELWQC94+skMGca4a0L/f4R9vlr30XIPzk hZ3OWxXBJZDu/OXzLrHLxzGsK6M0aE9RHvYA1ARw= Subject: FAILED: patch "[PATCH] tty: port: fix tty_port_tty_vhangup() race" failed to apply to 6.12-stable tree To: johan@kernel.org,gregkh@linuxfoundation.org Cc: From: Date: Mon, 05 Oct 2026 10:50:50 +0200 Message-ID: <2026100549-shortcake-ecosphere-463d@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x b48820de8c1a596c5b99775524dfce73c6576c5d # git commit -s git send-email --to '' --in-reply-to '2026100549-shortcake-ecosphere-463d@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b48820de8c1a596c5b99775524dfce73c6576c5d Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Thu, 10 Sep 2026 14:51:14 +0200 Subject: [PATCH] tty: port: fix tty_port_tty_vhangup() race 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 diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c index ae33987207b6..b22ff9eb7778 100644 --- a/drivers/tty/tty_port.c +++ b/drivers/tty/tty_port.c @@ -340,19 +340,9 @@ 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; @@ -372,6 +362,23 @@ 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 @@ -385,36 +392,58 @@ 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); +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_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 23cad403bb8f..8d22c59c6f15 100644 --- a/include/linux/tty_port.h +++ b/include/linux/tty_port.h @@ -245,7 +245,8 @@ 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); @@ -264,25 +265,6 @@ 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);