ASoC: codecs: tx-macro: Fix for KASAN: slab-out-of-bounds

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 Vishnu Vardhan Rao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: Ravulapati Vishnu Vardhan Rao

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;
@@ -1064,7 +1064,8 @@ 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;
+	u8 decimator;
 	int tx_fs_rate;
 	struct tx_macro *tx = snd_soc_component_get_drvdata(component);
 
@@ -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)