2024-02-16 10:59:56

by Bartosz Golaszewski

Subject: [PATCH] gpio: cdev: fix a NULL-pointer dereference with DEBUG enabled

From: Bartosz Golaszewski <[email protected]>

We are actually passing the gc pointer to chip_dbg() so we have to
srcu_dereference() it.

Fixes: 8574b5b47610 ("gpio: cdev: use correct pointer accessors with SRCU")
Reported-by: Marek Szyprowski <[email protected]>
Closes: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Bartosz Golaszewski <[email protected]>
---
drivers/gpio/gpiolib-cdev.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 85037fa4925e..f384fa278764 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -2795,8 +2795,8 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)
return ret;

guard(srcu)(&gdev->srcu);
-
- if (!rcu_access_pointer(gdev->chip))
+ gc = srcu_dereference(gdev->chip, &gdev->srcu);
+ if (!gc)
return -ENODEV;

chip_dbg(gc, "added GPIO chardev (%d:%d)\n", MAJOR(devt), gdev->id);
--
2.40.1

2024-02-16 12:37:35

by Marek Szyprowski

Subject: Re: [PATCH] gpio: cdev: fix a NULL-pointer dereference with DEBUG enabled

On 16.02.2024 11:59, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <[email protected]>
>
> We are actually passing the gc pointer to chip_dbg() so we have to
> srcu_dereference() it.
>
> Fixes: 8574b5b47610 ("gpio: cdev: use correct pointer accessors with SRCU")
> Reported-by: Marek Szyprowski <[email protected]>
> Closes: https://lore.kernel.org/lkml/[email protected]/
> Signed-off-by: Bartosz Golaszewski <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
> ---
> drivers/gpio/gpiolib-cdev.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> index 85037fa4925e..f384fa278764 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -2795,8 +2795,8 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)
> return ret;
>
> guard(srcu)(&gdev->srcu);
> -
> - if (!rcu_access_pointer(gdev->chip))
> + gc = srcu_dereference(gdev->chip, &gdev->srcu);
> + if (!gc)
> return -ENODEV;
>
> chip_dbg(gc, "added GPIO chardev (%d:%d)\n", MAJOR(devt), gdev->id);

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

2024-02-16 14:00:34

by Bartosz Golaszewski

Subject: Re: [PATCH] gpio: cdev: fix a NULL-pointer dereference with DEBUG enabled

On Fri, Feb 16, 2024 at 1:35 PM Marek Szyprowski
<[email protected]> wrote:
>
> On 16.02.2024 11:59, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <[email protected]>
> >
> > We are actually passing the gc pointer to chip_dbg() so we have to
> > srcu_dereference() it.
> >
> > Fixes: 8574b5b47610 ("gpio: cdev: use correct pointer accessors with SRCU")
> > Reported-by: Marek Szyprowski <[email protected]>
> > Closes: https://lore.kernel.org/lkml/[email protected]/
> > Signed-off-by: Bartosz Golaszewski <[email protected]>
> Tested-by: Marek Szyprowski <[email protected]>

Thanks, patch applied.

Bart

[snip]