ALSA: usb-audio: scarlett2: Use struct_size() helper in scarlett2_usb()

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>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220120211600.GA28841@embeddedor
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/mixer_scarlett_gen2.c b/sound/usb/mixer_scarlett_gen2.c
index 53ebabf42472224ee1dee0eeea5e8f7879c4739c..7ff8a4817c672cc133a82162138198fedeebf6f7 100644 (file)
--- 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;