Re: FAILED: patch "[PATCH] gpio: fix gpio-device list corruption" failed to apply to 5.11-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Mar 12, 2021 at 09:47:24AM +0100, Johan Hovold wrote:
> 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@vger.kernel.org>.
> 
> > ------------------ original commit in Linus's tree ------------------
> > 
> > From cf25ef6b631c6fc6c0435fc91eba8734cca20511 Mon Sep 17 00:00:00 2001
> > From: Johan Hovold <johan@kernel.org>
> > 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@vger.kernel.org      # 4.6
> > Reviewed-by: Saravana Kannan <saravanak@google.com>
> > Signed-off-by: Johan Hovold <johan@kernel.org>
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > 
> > 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.

Thanks for the backport, also added to 5.10.y

greg k-h