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 evdev_client.

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

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/input/evdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 95f90699d2b1..51e0c4954600 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -50,7 +50,7 @@ struct evdev_client {
 	bool revoked;
 	unsigned long *evmasks[EV_CNT];
 	unsigned int bufsize;
-	struct input_event buffer[];
+	struct input_event buffer[] __counted_by(bufsize);
 };
 
 static size_t evdev_get_mask_cnt(unsigned int type)
-- 
2.34.1

On Fri, Sep 22, 2023 at 10:50:28AM -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 evdev_client.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: linux-input@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Applied, thank you.

-- 
Dmitry

On 9/22/23 11:50, 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 evdev_client.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: linux-input@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
-- 
Gustavo

> ---
>   drivers/input/evdev.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index 95f90699d2b1..51e0c4954600 100644
> --- a/drivers/input/evdev.c
> +++ b/drivers/input/evdev.c
> @@ -50,7 +50,7 @@ struct evdev_client {
>   	bool revoked;
>   	unsigned long *evmasks[EV_CNT];
>   	unsigned int bufsize;
> -	struct input_event buffer[];
> +	struct input_event buffer[] __counted_by(bufsize);
>   };
>   
>   static size_t evdev_get_mask_cnt(unsigned int type)