FAILED: patch "[PATCH] tty: tty_port: restore TTY_IO_ERROR on activation failure" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 56964f6a31238fb41d5830bb42520c5b10ff7d8f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026100522-tidings-ouch-9669@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 56964f6a31238fb41d5830bb42520c5b10ff7d8f Mon Sep 17 00:00:00 2001
From: Johan Hovold <[email protected]>
Date: Tue, 8 Sep 2026 10:40:00 +0200
Subject: [PATCH] tty: tty_port: restore TTY_IO_ERROR on activation failure

Make sure to restore the TTY_IO_ERROR flag if activation fails to prevent I/O attempts on a port that is gone or powered down.

This specifically avoids issues like kernel panic due to unclocked accesses or NULL-pointer dereferences when accessing powered down or deregistered ports when a TTY ioctl races with hangup and open.

Note that the flag is set again in tty_port_close() but not restoring it on activation failure leaves a window where drivers fail to handle the ioctl-hangup race.

index 54359310e293..ae33987207b6 100644
@@ -767,8 +767,10 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
 		clear_bit(TTY_IO_ERROR, &tty->flags);
 		if (port->ops->activate) {
 			int retval = port->ops->activate(port, tty);
-			if (retval)
+			if (retval) {
+				set_bit(TTY_IO_ERROR, &tty->flags);
 				return retval;
+			}
 		}
 		tty_port_set_initialized(port, true);
 	}

From: Johan Hovold <[email protected]>

[ Upstream commit 56964f6a31238fb41d5830bb42520c5b10ff7d8f ]

Make sure to restore the TTY_IO_ERROR flag if activation fails to prevent I/O attempts on a port that is gone or powered down.

This specifically avoids issues like kernel panic due to unclocked accesses or NULL-pointer dereferences when accessing powered down or deregistered ports when a TTY ioctl races with hangup and open.

Note that the flag is set again in tty_port_close() but not restoring it on activation failure leaves a window where drivers fail to handle the ioctl-hangup race.

---
 drivers/tty/tty_port.c | 1 +
 1 file changed, 1 insertion(+)

index 494500c453ccb..6f3b4eeb44b38 100644
@@ -783,6 +783,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
 			int retval = port->ops->activate(port, tty);
 
 			if (retval) {
+				set_bit(TTY_IO_ERROR, &tty->flags);
 				mutex_unlock(&port->mutex);
 				return retval;
 			}

2.53.0