FAILED: patch "[PATCH] serial: imx: serialize imx_uart_ports[] lifetime" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] serial: imx: serialize imx_uart_ports[] lifetime" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 8b0b29fdcb47907ae0296b8fe829e918e05e300f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090333-scared-direness-4881@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 8b0b29fdcb47907ae0296b8fe829e918e05e300f Mon Sep 17 00:00:00 2001
From: Karl Mehltretter <kmehltretter@gmail.com>
Date: Fri, 31 Jul 2026 20:18:44 +0200
Subject: [PATCH] serial: imx: serialize imx_uart_ports[] lifetime

imx_uart_probe() publishes its devm-allocated port in imx_uart_ports[]
before uart_add_one_port() because console setup uses the table. The entry
is not cleared when adding the port fails or after removal, leaving a
dangling pointer.

A sibling probe can register the shared console through that stale entry.
This was reproduced under KASAN on QEMU mcimx6ul-evk by unbinding a
sibling UART, unbinding the console UART and rebinding the sibling.

Keep the entry valid through uart_remove_one_port(), then clear it. Protect
port addition and removal together with their table updates so sibling
operations cannot interleave. Reject an occupied slot rather than
clobbering an active port during a duplicate-line probe.

Fixes: dbff4e9ea2e8 ("IMX UART: remove statically initialized tables")
Fixes: 9f322ad064f9 ("imx: serial: handle initialisation failure correctly")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://lore.kernel.org/all/20260719162850.043B41F000E9@smtp.kernel.org
Link: https://lore.kernel.org/all/20260719222501.CB4CB1F000E9@smtp.kernel.org
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-fable-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260731181844.11330-6-kmehltretter@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 95fdb60e06a7..513dbe95f7e9 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -22,6 +22,7 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/ktime.h>
+#include <linux/mutex.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/rational.h>
 #include <linux/slab.h>
@@ -2080,6 +2081,9 @@ static const struct uart_ops imx_uart_pops = {
 
 static struct imx_port *imx_uart_ports[UART_NR];
 
+/* Held across uart_add/remove_one_port(); console callbacks must not take it. */
+static DEFINE_MUTEX(imx_uart_ports_lock);
+
 #if IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE)
 static void imx_uart_console_putchar(struct uart_port *port, unsigned char ch)
 {
@@ -2621,11 +2625,19 @@ static int imx_uart_probe(struct platform_device *pdev)
 			goto err_clk;
 	}
 
-	imx_uart_ports[sport->port.line] = sport;
-
 	platform_set_drvdata(pdev, sport);
 
-	ret = uart_add_one_port(&imx_uart_uart_driver, &sport->port);
+	scoped_guard(mutex, &imx_uart_ports_lock) {
+		if (imx_uart_ports[sport->port.line]) {
+			ret = -EBUSY;
+		} else {
+			imx_uart_ports[sport->port.line] = sport;
+			ret = uart_add_one_port(&imx_uart_uart_driver,
+						&sport->port);
+			if (ret)
+				imx_uart_ports[sport->port.line] = NULL;
+		}
+	}
 
 err_clk:
 	clk_disable_unprepare(sport->clk_ipg);
@@ -2637,7 +2649,9 @@ static void imx_uart_remove(struct platform_device *pdev)
 {
 	struct imx_port *sport = platform_get_drvdata(pdev);
 
+	guard(mutex)(&imx_uart_ports_lock);
 	uart_remove_one_port(&imx_uart_uart_driver, &sport->port);
+	imx_uart_ports[sport->port.line] = NULL;
 }
 
 static void imx_uart_restore_context(struct imx_port *sport)

[PATCH 5.15.y 1/2] serial: imx: Convert to platform remove callback returning void

[Sasha Levin]

From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

[ Upstream commit c066f87314b7fbbf4d72d38957436a98e7b7e503 ]

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.

To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20231110152927.70601-18-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 8b0b29fdcb47 ("serial: imx: serialize imx_uart_ports[] lifetime")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/imx.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index b9ef426d5aae3..ba64da1ca7b19 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2484,11 +2484,11 @@ static int imx_uart_probe(struct platform_device *pdev)
 	return ret;
 }
 
-static int imx_uart_remove(struct platform_device *pdev)
+static void imx_uart_remove(struct platform_device *pdev)
 {
 	struct imx_port *sport = platform_get_drvdata(pdev);
 
-	return uart_remove_one_port(&imx_uart_uart_driver, &sport->port);
+	uart_remove_one_port(&imx_uart_uart_driver, &sport->port);
 }
 
 static void imx_uart_restore_context(struct imx_port *sport)
@@ -2655,7 +2655,7 @@ static const struct dev_pm_ops imx_uart_pm_ops = {
 
 static struct platform_driver imx_uart_platform_driver = {
 	.probe = imx_uart_probe,
-	.remove = imx_uart_remove,
+	.remove_new = imx_uart_remove,
 
 	.driver = {
 		.name = "imx-uart",
-- 
2.53.0

[PATCH 5.15.y 2/2] serial: imx: serialize imx_uart_ports[] lifetime

[Sasha Levin]

From: Karl Mehltretter <kmehltretter@gmail.com>

[ Upstream commit 8b0b29fdcb47907ae0296b8fe829e918e05e300f ]

imx_uart_probe() publishes its devm-allocated port in imx_uart_ports[]
before uart_add_one_port() because console setup uses the table. The entry
is not cleared when adding the port fails or after removal, leaving a
dangling pointer.

A sibling probe can register the shared console through that stale entry.
This was reproduced under KASAN on QEMU mcimx6ul-evk by unbinding a
sibling UART, unbinding the console UART and rebinding the sibling.

Keep the entry valid through uart_remove_one_port(), then clear it. Protect
port addition and removal together with their table updates so sibling
operations cannot interleave. Reject an occupied slot rather than
clobbering an active port during a duplicate-line probe.

Fixes: dbff4e9ea2e8 ("IMX UART: remove statically initialized tables")
Fixes: 9f322ad064f9 ("imx: serial: handle initialisation failure correctly")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://lore.kernel.org/all/20260719162850.043B41F000E9@smtp.kernel.org
Link: https://lore.kernel.org/all/20260719222501.CB4CB1F000E9@smtp.kernel.org
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-fable-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260731181844.11330-6-kmehltretter@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ replaced scoped_guard() with explicit mutex_lock()/mutex_unlock() calls for GNU89 compatibility ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/imx.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index ba64da1ca7b19..11338cb7b2112 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -21,6 +21,7 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/ktime.h>
+#include <linux/mutex.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/rational.h>
 #include <linux/slab.h>
@@ -2005,6 +2006,9 @@ static const struct uart_ops imx_uart_pops = {
 
 static struct imx_port *imx_uart_ports[UART_NR];
 
+/* Held across uart_add/remove_one_port(); console callbacks must not take it. */
+static DEFINE_MUTEX(imx_uart_ports_lock);
+
 #if IS_ENABLED(CONFIG_SERIAL_IMX_CONSOLE)
 static void imx_uart_console_putchar(struct uart_port *port, int ch)
 {
@@ -2472,11 +2476,18 @@ static int imx_uart_probe(struct platform_device *pdev)
 		}
 	}
 
-	imx_uart_ports[sport->port.line] = sport;
-
 	platform_set_drvdata(pdev, sport);
 
-	ret = uart_add_one_port(&imx_uart_uart_driver, &sport->port);
+	mutex_lock(&imx_uart_ports_lock);
+	if (imx_uart_ports[sport->port.line]) {
+		ret = -EBUSY;
+	} else {
+		imx_uart_ports[sport->port.line] = sport;
+		ret = uart_add_one_port(&imx_uart_uart_driver, &sport->port);
+		if (ret)
+			imx_uart_ports[sport->port.line] = NULL;
+	}
+	mutex_unlock(&imx_uart_ports_lock);
 
 err_clk:
 	clk_disable_unprepare(sport->clk_ipg);
@@ -2488,7 +2499,9 @@ static void imx_uart_remove(struct platform_device *pdev)
 {
 	struct imx_port *sport = platform_get_drvdata(pdev);
 
+	guard(mutex)(&imx_uart_ports_lock);
 	uart_remove_one_port(&imx_uart_uart_driver, &sport->port);
+	imx_uart_ports[sport->port.line] = NULL;
 }
 
 static void imx_uart_restore_context(struct imx_port *sport)
-- 
2.53.0