linux-kernel - [PATCH] ASoC: renesas: rz-ssi: Add a check for negative sample

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Message-ID: <e07c3dc5-d885-4b04-a742-71f42243f4fd@stanley.mountain>
Date: Wed, 8 Jan 2025 12:28:46 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>, linux-sound@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH] ASoC: renesas: rz-ssi: Add a check for negative sample_space

My static checker rule complains about this code.  The concern is that
if "sample_space" is negative then the "sample_space >= runtime->channels"
condition will not work as intended because it will be type promoted to a
high unsigned int value.

strm->fifo_sample_size is SSI_FIFO_DEPTH (32).  The SSIFSR_TDC_MASK is
0x3f.  Without any further context it does seem like a reasonable warning
and it can't hurt to add a check for negatives.

Cc: stable@...r.kernel.org
Fixes: 03e786bd4341 ("ASoC: sh: Add RZ/G2L SSIF-2 driver")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 sound/soc/renesas/rz-ssi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/soc/renesas/rz-ssi.c b/sound/soc/renesas/rz-ssi.c
index d48e2e7356b6..3a0af4ca7ab6 100644
--- a/sound/soc/renesas/rz-ssi.c
+++ b/sound/soc/renesas/rz-ssi.c
@@ -521,6 +521,8 @@ static int rz_ssi_pio_send(struct rz_ssi_priv *ssi, struct rz_ssi_stream *strm)
 	sample_space = strm->fifo_sample_size;
 	ssifsr = rz_ssi_reg_readl(ssi, SSIFSR);
 	sample_space -= (ssifsr >> SSIFSR_TDC_SHIFT) & SSIFSR_TDC_MASK;
+	if (sample_space < 0)
+		return -EINVAL;
 
 	/* Only add full frames at a time */
 	while (frames_left && (sample_space >= runtime->channels)) {
-- 
2.45.2