FAILED: patch "[PATCH] serial: don't use uninitialized value in uart_poll_init()" 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 d0009a32c9e4e083358092f3c97e3c6e803a8930
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024100108-attention-muppet-0778@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

d0009a32c9e4 ("serial: don't use uninitialized value in uart_poll_init()")
788aeef392d2 ("tty: serial: kgdboc: Fix 8250_* kgdb over serial")

thanks,

greg k-h

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

From d0009a32c9e4e083358092f3c97e3c6e803a8930 Mon Sep 17 00:00:00 2001
From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Date: Mon, 5 Aug 2024 12:20:36 +0200
Subject: [PATCH] serial: don't use uninitialized value in uart_poll_init()
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

Coverity reports (as CID 1536978) that uart_poll_init() passes
uninitialized pm_state to uart_change_pm(). It is in case the first 'if'
takes the true branch (does "goto out;").

Fix this and simplify the function by simple guard(mutex). The code
needs no labels after this at all. And it is pretty clear that the code
has not fiddled with pm_state at that point.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Fixes: 5e227ef2aa38 (serial: uart_poll_init() should power on the UART)
Cc: stable@vger.kernel.org
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20240805102046.307511-4-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 83c5bccc5086..e0aac155dca2 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2690,14 +2690,13 @@ static int uart_poll_init(struct tty_driver *driver, int line, char *options)
 	int ret = 0;
 
 	tport = &state->port;
-	mutex_lock(&tport->mutex);
+
+	guard(mutex)(&tport->mutex);
 
 	port = uart_port_check(state);
 	if (!port || port->type == PORT_UNKNOWN ||
-	    !(port->ops->poll_get_char && port->ops->poll_put_char)) {
-		ret = -1;
-		goto out;
-	}
+	    !(port->ops->poll_get_char && port->ops->poll_put_char))
+		return -1;
 
 	pm_state = state->pm_state;
 	uart_change_pm(state, UART_PM_STATE_ON);
@@ -2717,10 +2716,10 @@ static int uart_poll_init(struct tty_driver *driver, int line, char *options)
 		ret = uart_set_options(port, NULL, baud, parity, bits, flow);
 		console_list_unlock();
 	}
-out:
+
 	if (ret)
 		uart_change_pm(state, pm_state);
-	mutex_unlock(&tport->mutex);
+
 	return ret;
 }