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SubjectRe: [PATCH] usb: gadget: f_midi: Annotate struct f_midi with __counted_by
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On 9/15/23 13:59, 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 f_midi.
> 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: John Keeping <john@keeping.me.uk>
> Cc: Peter Chen <peter.chen@nxp.com>
> Cc: Hulk Robot <hulkci@huawei.com>
> Cc: Allen Pais <allen.lkml@gmail.com>
> Cc: Will McVicker <willmcvicker@google.com>
> Cc: Davidlohr Bueso <dave@stgolabs.net>
> Cc: Zhang Qilong <zhangqilong3@huawei.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_midi.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
> index 2d02f25f9597..033e347554db 100644
> --- a/drivers/usb/gadget/function/f_midi.c
> +++ b/drivers/usb/gadget/function/f_midi.c
> @@ -99,7 +99,7 @@ struct f_midi {
> unsigned int in_last_port;
> unsigned char free_ref;
>
> - struct gmidi_in_port in_ports_array[/* in_ports */];
> + struct gmidi_in_port in_ports_array[] __counted_by(in_ports);
> };
>
> static inline struct f_midi *func_to_midi(struct usb_function *f)
> @@ -1349,6 +1349,7 @@ static struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
> status = -ENOMEM;
> goto setup_fail;
> }
> + midi->in_ports = opts->in_ports;
>
> for (i = 0; i < opts->in_ports; i++)
> midi->in_ports_array[i].cable = i;
> @@ -1359,7 +1360,6 @@ static struct usb_function *f_midi_alloc(struct usb_function_instance *fi)
> status = -ENOMEM;
> goto midi_free;
> }
> - midi->in_ports = opts->in_ports;
> midi->out_ports = opts->out_ports;
> midi->index = opts->index;
> midi->buflen = opts->buflen;

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