From:   Ravulapati Vishnu Vardhan Rao <quic_visr@quicinc.com>
CC:     <quic_visr@quicinc.com>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Banajit Goswami <bgoswami@quicinc.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        "moderated list:QCOM AUDIO (ASoC) DRIVERS" 
        <alsa-devel@alsa-project.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: [PATCH] ASoC: codecs: tx-macro: Fix for KASAN: slab-out-of-bounds
Date:   Fri, 3 Mar 2023 18:27:16 +0530
Message-ID: <20230303125717.29196-1-quic_visr@quicinc.com>
MIME-Version: 1.0
Content-Type: text/plain
To:     unlisted-recipients:; (no To-header on input)
Precedence: bulk

From: visr <quic_visr@quicinc.com>

When we run syzkaller we get below Out of Bound.
"KASAN: slab-out-of-bounds Read in regcache_flat_read"

Below is the backtrace of the issue:

dump_backtrace+0x0/0x4c8
show_stack+0x34/0x44
dump_stack_lvl+0xd8/0x118
print_address_description+0x30/0x2d8
kasan_report+0x158/0x198
__asan_report_load4_noabort+0x44/0x50
regcache_flat_read+0x10c/0x110
regcache_read+0xf4/0x180
_regmap_read+0xc4/0x278
_regmap_update_bits+0x130/0x290
regmap_update_bits_base+0xc0/0x15c
snd_soc_component_update_bits+0xa8/0x22c
snd_soc_component_write_field+0x68/0xd4
tx_macro_digital_mute+0xec/0x140

Actually There is no need to have decimator with 32 bits.
By limiting the variable with short type u8 issue is resolved.

Signed-off-by: RAVULAPATI VISHNUVARDHAN RAO <quic_visr@quicinc.com>
---
 sound/soc/codecs/lpass-tx-macro.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/sound/soc/codecs/lpass-tx-macro.c b/sound/soc/codecs/lpass-tx-macro.c
index bf27bdd5be20..73014fa6e4b8 100644
--- a/sound/soc/codecs/lpass-tx-macro.c
+++ b/sound/soc/codecs/lpass-tx-macro.c
@@ -242,7 +242,7 @@ enum {
 
 struct tx_mute_work {
 	struct tx_macro *tx;
-	u32 decimator;
+	u8 decimator;
 	struct delayed_work dwork;
 };
 
@@ -635,7 +635,7 @@ static int tx_macro_mclk_enable(struct tx_macro *tx,
 	return 0;
 }
 
-static bool is_amic_enabled(struct snd_soc_component *component, int decimator)
+static bool is_amic_enabled(struct snd_soc_component *component, u8 decimator)
 {
 	u16 adc_mux_reg, adc_reg, adc_n;
 
@@ -849,7 +849,7 @@ static int tx_macro_enable_dec(struct snd_soc_dapm_widget *w,
 			       struct snd_kcontrol *kcontrol, int event)
 {
 	struct snd_soc_component *component = snd_soc_dapm_to_component(w->dapm);
-	unsigned int decimator;
+	u8 decimator;
 	u16 tx_vol_ctl_reg, dec_cfg_reg, hpf_gate_reg, tx_gain_ctl_reg;
 	u8 hpf_cut_off_freq;
 	int hpf_delay = TX_MACRO_DMIC_HPF_DELAY_MS;
@@ -1064,9 +1064,10 @@ static int tx_macro_hw_params(struct snd_pcm_substream *substream,
 			      struct snd_soc_dai *dai)
 {
 	struct snd_soc_component *component = dai->component;
-	u32 decimator, sample_rate;
+	u32 sample_rate;
 	int tx_fs_rate;
 	struct tx_macro *tx = snd_soc_component_get_drvdata(component);
+	u8 decimator = 0;
 
 	sample_rate = params_rate(params);
 	switch (sample_rate) {
@@ -1128,7 +1129,7 @@ static int tx_macro_digital_mute(struct snd_soc_dai *dai, int mute, int stream)
 {
 	struct snd_soc_component *component = dai->component;
 	struct tx_macro *tx = snd_soc_component_get_drvdata(component);
-	u16 decimator;
+	u8 decimator;
 
 	/* active decimator not set yet */
 	if (tx->active_decimator[dai->id] == -1)
-- 
2.17.1