FAILED: patch "[PATCH] tty: tty_port: restore TTY_IO_ERROR on activation failure" failed to apply to 6.6-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.6-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 <stable@vger.kernel.org>.

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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 56964f6a31238fb41d5830bb42520c5b10ff7d8f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026100521-halogen-alphabet-2d56@gregkh' --subject-prefix 'PATCH 6.6.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 <johan@kernel.org>
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.

Fixes: a9a37ec33a1b ("tty: tty_port: Move the IO_ERROR clear")
Cc: stable <stable@kernel.org>  # 2.6.33
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20260908084000.218528-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 54359310e293..ae33987207b6 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -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);
 	}