FAILED: patch "[PATCH] serial: core: shut down initialized port on removal" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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 <[email protected]>.

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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 810d467c11f0c85107874d08dfdd11acba6aa0c0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026110440-crouch-oblivion-2771@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 810d467c11f0c85107874d08dfdd11acba6aa0c0 Mon Sep 17 00:00:00 2001
From: Igor Putko <[email protected]>
Date: Sat, 3 Oct 2026 19:33:37 +0300
Subject: [PATCH] serial: core: shut down initialized port on removal

When a serial port configured as a console is opened and subsequently closed, tty_port_shutdown() skips invoking port->ops->shutdown() because port->console is true. As a result, tty_port_initialized() remains true and the port's interrupt handler stays registered in the irq subsystem.

If the underlying device is later unbound or removed (e.g. via sysfs driver unbind or device hot-unplug), serial_core_remove_one_port() unregisters the console, frees uport->name via kfree(), and tears down the port without shutting it down or freeing its IRQ. Consequently, the irqaction descriptor remains registered in genirq with action->name pointing to freed memory.

This triggers a use-after-free read whenever genirq accesses action->name, such as when reading /proc/interrupts:

  BUG: KASAN: slab-use-after-free in string+0x476/0x570
  Call Trace:
   string+0x476/0x570
   vsnprintf+0x422/0x1300
   seq_printf+0x...
   show_interrupts+...

Fix this by acquiring port->mutex in serial_core_remove_one_port() after console unregistration, clearing port->console under the mutex to prevent data races with concurrent tty_port_shutdown(), and invoking uart_shutdown(NULL, state) if the port remains initialized. This ensures that port->ops->shutdown() is called and the IRQ is freed before kfree(uport->name).

index 319a4b427f3a..05450529871e 100644
@@ -3239,6 +3239,13 @@ static void serial_core_remove_one_port(struct uart_driver *drv,
 	if (uart_console(uport))
 		unregister_console(uport->cons);
 
+	scoped_guard(mutex, &port->mutex) {
+		port->console = false;
+
+		if (tty_port_initialized(port))
+			uart_shutdown(NULL, state);
+	}
+
 	/*
 	 * Free the port IO and memory resources, if any.
 	 */

From: Igor Putko <[email protected]>

[ Upstream commit 810d467c11f0c85107874d08dfdd11acba6aa0c0 ]

When a serial port configured as a console is opened and subsequently closed, tty_port_shutdown() skips invoking port->ops->shutdown() because port->console is true. As a result, tty_port_initialized() remains true and the port's interrupt handler stays registered in the irq subsystem.

If the underlying device is later unbound or removed (e.g. via sysfs driver unbind or device hot-unplug), serial_core_remove_one_port() unregisters the console, frees uport->name via kfree(), and tears down the port without shutting it down or freeing its IRQ. Consequently, the irqaction descriptor remains registered in genirq with action->name pointing to freed memory.

This triggers a use-after-free read whenever genirq accesses action->name, such as when reading /proc/interrupts:

  BUG: KASAN: slab-use-after-free in string+0x476/0x570
  Call Trace:
   string+0x476/0x570
   vsnprintf+0x422/0x1300
   seq_printf+0x...
   show_interrupts+...

Fix this by acquiring port->mutex in serial_core_remove_one_port() after console unregistration, clearing port->console under the mutex to prevent data races with concurrent tty_port_shutdown(), and invoking uart_shutdown(NULL, state) if the port remains initialized. This ensures that port->ops->shutdown() is called and the IRQ is freed before kfree(uport->name).

---
 drivers/tty/serial/serial_core.c | 7 +++++++
 1 file changed, 7 insertions(+)

index 4ffa682203166..ada412490668e 100644
@@ -3090,6 +3090,13 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
 	if (uart_console(uport))
 		unregister_console(uport->cons);
 
+	mutex_lock(&port->mutex);
+	port->console = false;
+
+	if (tty_port_initialized(port))
+		uart_shutdown(NULL, state);
+	mutex_unlock(&port->mutex);
+
 	/*
 	 * Free the port IO and memory resources, if any.
 	 */

2.53.0