On Thu, Mar 11, 2021 at 06:41:41PM +0100, Greg Kroah-Hartman wrote:
>
> The patch below does not apply to the 5.11-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@xxxxxxxxxxxxxxx>.
> ------------------ original commit in Linus's tree ------------------
>
> From cf25ef6b631c6fc6c0435fc91eba8734cca20511 Mon Sep 17 00:00:00 2001
> From: Johan Hovold <johan@xxxxxxxxxx>
> Date: Mon, 1 Mar 2021 10:05:19 +0100
> Subject: [PATCH] gpio: fix gpio-device list corruption
>
> Make sure to hold the gpio_lock when removing the gpio device from the
> gpio_devices list (when dropping the last reference) to avoid corrupting
> the list when there are concurrent accesses.
>
> Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
> Cc: stable@xxxxxxxxxxxxxxx # 4.6
> Reviewed-by: Saravana Kannan <saravanak@xxxxxxxxxx>
> Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 6e0572515d02..4253837f870b 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -475,8 +475,12 @@ EXPORT_SYMBOL_GPL(gpiochip_line_is_valid);
> static void gpiodevice_release(struct device *dev)
> {
> struct gpio_device *gdev = container_of(dev, struct gpio_device, dev);
> + unsigned long flags;
>
> + spin_lock_irqsave(&gpio_lock, flags);
> list_del(&gdev->list);
> + spin_unlock_irqrestore(&gpio_lock, flags);
> +
> ida_free(&gpio_ida, gdev->id);
> kfree_const(gdev->label);
> kfree(gdev->descs);
>
Bah, that's because of a6112998ee45 ("gpio: fix
NULL-deref-on-deregistration regression") which is strictly only needed
in 5.12 even if it could be backported (the commit message might be a
bit confusing though).
I should have reversed the order of these two.
Below is a backport to 5.11.
Johan
>From 7599320f36bb5273844dfb749861a5361d8aa5b7 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@xxxxxxxxxx>
Date: Mon, 1 Mar 2021 10:05:19 +0100
Subject: [PATCH] gpio: fix gpio-device list corruption
Make sure to hold the gpio_lock when removing the gpio device from the
gpio_devices list (when dropping the last reference) to avoid corrupting
the list when there are concurrent accesses.
Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
Cc: stable@xxxxxxxxxxxxxxx # 4.6
Reviewed-by: Saravana Kannan <saravanak@xxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
[ johan: adjust context to 5.11 ]
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
drivers/gpio/gpiolib.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index adf55db080d8..0069b115928c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -475,8 +475,12 @@ EXPORT_SYMBOL_GPL(gpiochip_line_is_valid);
static void gpiodevice_release(struct device *dev)
{
struct gpio_device *gdev = dev_get_drvdata(dev);
+ unsigned long flags;
+ spin_lock_irqsave(&gpio_lock, flags);
list_del(&gdev->list);
+ spin_unlock_irqrestore(&gpio_lock, flags);
+
ida_free(&gpio_ida, gdev->id);
kfree_const(gdev->label);
kfree(gdev->descs);
--
2.26.2
