[PATCH] gpiolib: cdev: Annotate struct linereq with __counted_by

[PATCH] gpiolib: cdev: Annotate struct linereq with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct linereq.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: linux-gpio@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 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 e39d344feb28..31fc71a612c2 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -572,7 +572,7 @@ struct linereq {
 	DECLARE_KFIFO_PTR(events, struct gpio_v2_line_event);
 	atomic_t seqno;
 	struct mutex config_mutex;
-	struct line lines[];
+	struct line lines[] __counted_by(num_lines);
 };
 
 #define GPIO_V2_LINE_BIAS_FLAGS \
@@ -1656,6 +1656,7 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
 	lr = kzalloc(struct_size(lr, lines, ulr.num_lines), GFP_KERNEL);
 	if (!lr)
 		return -ENOMEM;
+	lr->num_lines = ulr.num_lines;
 
 	lr->gdev = gpio_device_get(gdev);
 
@@ -1684,7 +1685,6 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
 		lr->event_buffer_size = GPIO_V2_LINES_MAX * 16;
 
 	atomic_set(&lr->seqno, 0);
-	lr->num_lines = ulr.num_lines;
 
 	/* Request each GPIO */
 	for (i = 0; i < ulr.num_lines; i++) {
-- 
2.34.1

Re: [PATCH] gpiolib: cdev: Annotate struct linereq with __counted_by

[Gustavo A. R. Silva]

On 9/22/23 11:52, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct linereq.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: linux-gpio@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
-- 
Gustavo

> ---
>   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 e39d344feb28..31fc71a612c2 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -572,7 +572,7 @@ struct linereq {
>   	DECLARE_KFIFO_PTR(events, struct gpio_v2_line_event);
>   	atomic_t seqno;
>   	struct mutex config_mutex;
> -	struct line lines[];
> +	struct line lines[] __counted_by(num_lines);
>   };
>   
>   #define GPIO_V2_LINE_BIAS_FLAGS \
> @@ -1656,6 +1656,7 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
>   	lr = kzalloc(struct_size(lr, lines, ulr.num_lines), GFP_KERNEL);
>   	if (!lr)
>   		return -ENOMEM;
> +	lr->num_lines = ulr.num_lines;
>   
>   	lr->gdev = gpio_device_get(gdev);
>   
> @@ -1684,7 +1685,6 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
>   		lr->event_buffer_size = GPIO_V2_LINES_MAX * 16;
>   
>   	atomic_set(&lr->seqno, 0);
> -	lr->num_lines = ulr.num_lines;
>   
>   	/* Request each GPIO */
>   	for (i = 0; i < ulr.num_lines; i++) {

Re: [PATCH] gpiolib: cdev: Annotate struct linereq with __counted_by

[Linus Walleij]

On Fri, Sep 22, 2023 at 7:52 PM Kees Cook <keescook@chromium.org> wrote:

> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct linereq.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: linux-gpio@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

That's neat!
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: [PATCH] gpiolib: cdev: Annotate struct linereq with __counted_by

[Andy Shevchenko]

On Fri, Sep 22, 2023 at 10:52:03AM -0700, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct linereq.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.

Ah, hadn't taken into account in my patch, so, Bart, feel free to ignore mine
and apply this one.

Reviewed-by: Andy Shevchenko <andy@kernel.org>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] gpiolib: cdev: Annotate struct linereq with __counted_by

[Bartosz Golaszewski]

On Fri, Sep 22, 2023 at 7:52 PM Kees Cook <keescook@chromium.org> wrote:
>
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct linereq.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: linux-gpio@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---

Applied, thanks!

Bart