linux-kernel - [PATCH 4.19 045/211] ALSA: i2c: ak4xxx-adda: Fix a possible null pointer dereference in build_adc

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Message-Id: <20191003154458.327220310@linuxfoundation.org>
Date:   Thu,  3 Oct 2019 17:51:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>,
        Takashi Iwai <tiwai@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 045/211] ALSA: i2c: ak4xxx-adda: Fix a possible null pointer dereference in build_adc_controls()

From: Jia-Ju Bai <baijiaju1990@...il.com>

[ Upstream commit 2127c01b7f63b06a21559f56a8c81a3c6535bd1a ]

In build_adc_controls(), there is an if statement on line 773 to check
whether ak->adc_info is NULL:
    if (! ak->adc_info ||
        ! ak->adc_info[mixer_ch].switch_name)

When ak->adc_info is NULL, it is used on line 792:
    knew.name = ak->adc_info[mixer_ch].selector_name;

Thus, a possible null-pointer dereference may occur.

To fix this bug, referring to lines 773 and 774, ak->adc_info
and ak->adc_info[mixer_ch].selector_name are checked before being used.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/i2c/other/ak4xxx-adda.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/sound/i2c/other/ak4xxx-adda.c b/sound/i2c/other/ak4xxx-adda.c
index 7f2761a2e7c8c..971197c34fcef 100644
--- a/sound/i2c/other/ak4xxx-adda.c
+++ b/sound/i2c/other/ak4xxx-adda.c
@@ -789,11 +789,12 @@ static int build_adc_controls(struct snd_akm4xxx *ak)
 				return err;
 
 			memset(&knew, 0, sizeof(knew));
-			knew.name = ak->adc_info[mixer_ch].selector_name;
-			if (!knew.name) {
+			if (!ak->adc_info ||
+				!ak->adc_info[mixer_ch].selector_name) {
 				knew.name = "Capture Channel";
 				knew.index = mixer_ch + ak->idx_offset * 2;
-			}
+			} else
+				knew.name = ak->adc_info[mixer_ch].selector_name;
 
 			knew.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
 			knew.info = ak4xxx_capture_source_info;
-- 
2.20.1