[PATCH v2][next] ALSA: usb-audio: scarlett2: Use struct_size() helper in scarlett2_usb()

[PATCH v2][next] ALSA: usb-audio: scarlett2: Use struct_size() helper in scarlett2_usb()

[Gustavo A. R. Silva]

Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows that,
in the worst scenario, could lead to heap overflows.

Also, address the following sparse warnings:
sound/usb/mixer_scarlett_gen2.c:1064:28: warning: using sizeof on a flexible structure
sound/usb/mixer_scarlett_gen2.c:1065:29: warning: using sizeof on a flexible structure

Link: https://github.com/KSPP/linux/issues/174
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
 - Use correct format specifier %zu for type size_t argument.

 sound/usb/mixer_scarlett_gen2.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c
index 53ebabf42472..7ff8a4817c67 100644
--- a/sound/usb/mixer_scarlett_gen2.c
+++ b/sound/usb/mixer_scarlett_gen2.c
@@ -1061,9 +1061,9 @@ static int scarlett2_usb(
 {
 	struct scarlett2_data *private = mixer->private_data;
 	struct usb_device *dev = mixer->chip->dev;
-	u16 req_buf_size = sizeof(struct scarlett2_usb_packet) + req_size;
-	u16 resp_buf_size = sizeof(struct scarlett2_usb_packet) + resp_size;
 	struct scarlett2_usb_packet *req, *resp = NULL;
+	size_t req_buf_size = struct_size(req, data, req_size);
+	size_t resp_buf_size = struct_size(resp, data, resp_size);
 	int err;
 
 	req = kmalloc(req_buf_size, GFP_KERNEL);
@@ -1111,7 +1111,7 @@ static int scarlett2_usb(
 		usb_audio_err(
 			mixer->chip,
 			"Scarlett Gen 2/3 USB response result cmd %x was %d "
-			"expected %d\n",
+			"expected %zu\n",
 			cmd, err, resp_buf_size);
 		err = -EINVAL;
 		goto unlock;
-- 
2.27.0

Re: [PATCH v2][next] ALSA: usb-audio: scarlett2: Use struct_size() helper in scarlett2_usb()

[Kees Cook]

On Thu, Jan 20, 2022 at 03:16:00PM -0600, Gustavo A. R. Silva wrote:
> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worst scenario, could lead to heap overflows.
> 
> Also, address the following sparse warnings:
> sound/usb/mixer_scarlett_gen2.c:1064:28: warning: using sizeof on a flexible structure
> sound/usb/mixer_scarlett_gen2.c:1065:29: warning: using sizeof on a flexible structure
> 
> Link: https://github.com/KSPP/linux/issues/174
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Looks good to me!

Reviewed-by: Kees Cook <keescook@chromium.org>

> ---
> Changes in v2:
>  - Use correct format specifier %zu for type size_t argument.
> 
>  sound/usb/mixer_scarlett_gen2.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c
> index 53ebabf42472..7ff8a4817c67 100644
> --- a/sound/usb/mixer_scarlett_gen2.c
> +++ b/sound/usb/mixer_scarlett_gen2.c
> @@ -1061,9 +1061,9 @@ static int scarlett2_usb(
>  {
>  	struct scarlett2_data *private = mixer->private_data;
>  	struct usb_device *dev = mixer->chip->dev;
> -	u16 req_buf_size = sizeof(struct scarlett2_usb_packet) + req_size;
> -	u16 resp_buf_size = sizeof(struct scarlett2_usb_packet) + resp_size;
>  	struct scarlett2_usb_packet *req, *resp = NULL;
> +	size_t req_buf_size = struct_size(req, data, req_size);
> +	size_t resp_buf_size = struct_size(resp, data, resp_size);
>  	int err;
>  
>  	req = kmalloc(req_buf_size, GFP_KERNEL);
> @@ -1111,7 +1111,7 @@ static int scarlett2_usb(
>  		usb_audio_err(
>  			mixer->chip,
>  			"Scarlett Gen 2/3 USB response result cmd %x was %d "
> -			"expected %d\n",
> +			"expected %zu\n",
>  			cmd, err, resp_buf_size);
>  		err = -EINVAL;
>  		goto unlock;
> -- 
> 2.27.0
> 

-- 
Kees Cook

Re: [PATCH v2][next] ALSA: usb-audio: scarlett2: Use struct_size() helper in scarlett2_usb()

[Takashi Iwai]

On Thu, 20 Jan 2022 22:16:00 +0100,
Gustavo A. R. Silva wrote:
> 
> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worst scenario, could lead to heap overflows.
> 
> Also, address the following sparse warnings:
> sound/usb/mixer_scarlett_gen2.c:1064:28: warning: using sizeof on a flexible structure
> sound/usb/mixer_scarlett_gen2.c:1065:29: warning: using sizeof on a flexible structure
> 
> Link: https://github.com/KSPP/linux/issues/174
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes in v2:
>  - Use correct format specifier %zu for type size_t argument.

Applied now.  Thanks.


Takashi