[PATCH 5.15.y 1/3] ALSA: usx2y: Prefer struct_size over open coded arithmetic

[Sasha Levin <sashal@kernel.org>]

From: Len Baker <len.baker@gmx.com>

[ Upstream commit f02f2f1bf9d154148325eb60d74bdf199022ea52 ]

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

In this case this is not actually dynamic size: all the operands
involved in the calculation are constant values. However it is better to
refactor this anyway, just to keep the open-coded math idiom out of
code.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + size * count" in the kzalloc() function.

Also, take the opportunity to refactor the declaration variables to make
it more easy to read.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@gmx.com>
Link: https://lore.kernel.org/r/20210919133727.44694-1-len.baker@gmx.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Stable-dep-of: 36aa66de481d ("ALSA: hda/ext: preserve PPLCCTL bits when clearing reset")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 sound/usb/usx2y/usbusx2yaudio.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/sound/usb/usx2y/usbusx2yaudio.c b/sound/usb/usx2y/usbusx2yaudio.c
index a6ed4f0230b7f..3816d2d6723da 100644
--- a/sound/usb/usx2y/usbusx2yaudio.c
+++ b/sound/usb/usx2y/usbusx2yaudio.c
@@ -641,14 +641,15 @@ static void i_usx2y_04int(struct urb *urb)
 
 static int usx2y_rate_set(struct usx2ydev *usx2y, int rate)
 {
-	int			err = 0, i;
-	struct snd_usx2y_urb_seq	*us = NULL;
-	int			*usbdata = NULL;
-	const struct s_c2	*ra = rate == 48000 ? setrate_48000 : setrate_44100;
+	int err = 0, i;
+	struct snd_usx2y_urb_seq *us = NULL;
+	int *usbdata = NULL;
+	const struct s_c2 *ra = rate == 48000 ? setrate_48000 : setrate_44100;
 	struct urb *urb;
 
 	if (usx2y->rate != rate) {
-		us = kzalloc(sizeof(*us) + sizeof(struct urb *) * NOOF_SETRATE_URBS, GFP_KERNEL);
+		us = kzalloc(struct_size(us, urb, NOOF_SETRATE_URBS),
+			     GFP_KERNEL);
 		if (!us) {
 			err = -ENOMEM;
 			goto cleanup;
-- 
2.53.0