linux-hardening - Re: [PATCH] usb: gadget: f_fs: Annotate struct ffs_buffer with __counted

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Message-ID: <0b48fe61-7d05-1520-d77e-81ad39bc80b4@embeddedor.com>
Date:   Fri, 15 Sep 2023 14:21:58 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     John Keeping <john@...ping.me.uk>,
        Udipto Goswami <quic_ugoswami@...cinc.com>,
        Linyu Yuan <quic_linyyuan@...cinc.com>,
        linux-usb@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Krishna Kurapati <quic_kriskura@...cinc.com>,
        Jeff Layton <jlayton@...nel.org>,
        Uttkarsh Aggarwal <quic_uaggarwa@...cinc.com>,
        Yuta Hayama <hayama@...eo.co.jp>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: f_fs: Annotate struct ffs_buffer with
 __counted_by



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@...uxfoundation.org>
> Cc: John Keeping <john@...ping.me.uk>
> Cc: Udipto Goswami <quic_ugoswami@...cinc.com>
> Cc: Linyu Yuan <quic_linyyuan@...cinc.com>
> Cc: linux-usb@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.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 ***************************************************/