[PATCH] usb: gadget: f_fs: Annotate struct ffs_buffer with __counted_by

[PATCH] usb: gadget: f_fs: Annotate struct ffs_buffer 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 ffs_buffer.

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

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: John Keeping <john@keeping.me.uk>
Cc: Udipto Goswami <quic_ugoswami@quicinc.com>
Cc: Linyu Yuan <quic_linyyuan@quicinc.com>
Cc: linux-usb@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/usb/gadget/function/f_fs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 6e9ef35a43a7..af400d083777 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -202,7 +202,7 @@ struct ffs_epfile {
 struct ffs_buffer {
 	size_t length;
 	char *data;
-	char storage[];
+	char storage[] __counted_by(length);
 };
 
 /*  ffs_io_data structure ***************************************************/
-- 
2.34.1

Re: [PATCH] usb: gadget: f_fs: Annotate struct ffs_buffer with __counted_by

[Gustavo A. R. Silva]

On 9/15/23 13:58, 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 ffs_buffer.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: John Keeping <john@keeping.me.uk>
> Cc: Udipto Goswami <quic_ugoswami@quicinc.com>
> Cc: Linyu Yuan <quic_linyyuan@quicinc.com>
> Cc: linux-usb@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks
-- 
Gustavo

> ---
>   drivers/usb/gadget/function/f_fs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 6e9ef35a43a7..af400d083777 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -202,7 +202,7 @@ struct ffs_epfile {
>   struct ffs_buffer {
>   	size_t length;
>   	char *data;
> -	char storage[];
> +	char storage[] __counted_by(length);
>   };
>   
>   /*  ffs_io_data structure ***************************************************/

Re: [PATCH] usb: gadget: f_fs: Annotate struct ffs_buffer with __counted_by

[Kees Cook]

On Fri, 15 Sep 2023 12:58:49 -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 ffs_buffer.
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] usb: gadget: f_fs: Annotate struct ffs_buffer with __counted_by
      https://git.kernel.org/kees/c/84657a30a0c9

Take care,

-- 
Kees Cook