ALSA: i2c: ak4xxx-adda: Fix a possible null pointer dereference in build_adc_controls()

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@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/i2c/other/ak4xxx-adda.c b/sound/i2c/other/ak4xxx-adda.c
index 5f59316f982aec71f89de6d1bc91f18f5e7d3c39..7d15093844b9232fc83ccfc16c1225ee00b43168 100644 (file)
--- a/sound/i2c/other/ak4xxx-adda.c
+++ b/sound/i2c/other/ak4xxx-adda.c
@@ -775,11 +775,12 @@ 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;