[PATCH] usb: gadget: f_midi: Annotate struct f_midi with __counted_by

[PATCH] usb: gadget: f_midi: Annotate struct f_midi 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 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>
---
 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;
-- 
2.34.1

Re: [PATCH] usb: gadget: f_midi: Annotate struct f_midi with __counted_by

[Gustavo A. R. Silva]

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;

Re: [PATCH] usb: gadget: f_midi: Annotate struct f_midi with __counted_by

[Kees Cook]

On Fri, 15 Sep 2023 12:59:39 -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 f_midi.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] usb: gadget: f_midi: Annotate struct f_midi with __counted_by
      https://git.kernel.org/kees/c/cfe2af2d553f

Take care,

-- 
Kees Cook