ALSA: hda: Use scnprintf() for printing texts for sysfs/procfs

BugLink: https://bugs.launchpad.net/bugs/1868627

commit 44eeb081 upstream.

Some code in HD-audio driver calls snprintf() in a loop and still
expects that the return value were actually written size, while
snprintf() returns the expected would-be length instead.  When the
given buffer limit were small, this leads to a buffer overflow.

Use scnprintf() for addressing those issues.  It returns the actually
written size unlike snprintf().

Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200218091409.27162-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

sound/pci/hda/hda_codec.c

@@ -4098,7 +4098,7 @@ void snd_print_pcm_bits(int pcm, char *buf, int buflen)
 
 	for (i = 0, j = 0; i < ARRAY_SIZE(bits); i++)
 		if (pcm & (AC_SUPPCM_BITS_8 << i))
-			j += snprintf(buf + j, buflen - j,  " %d", bits[i]);
+			j += scnprintf(buf + j, buflen - j,  " %d", bits[i]);
 
 	buf[j] = '\0'; /* necessary when j == 0 */
 }

sound/pci/hda/hda_eld.c

@@ -385,7 +385,7 @@ static void hdmi_print_pcm_rates(int pcm, char *buf, int buflen)
 
 	for (i = 0, j = 0; i < ARRAY_SIZE(alsa_rates); i++)
 		if (pcm & (1 << i))
-			j += snprintf(buf + j, buflen - j,  " %d",
+			j += scnprintf(buf + j, buflen - j,  " %d",
 				alsa_rates[i]);
 
 	buf[j] = '\0'; /* necessary when j == 0 */

sound/pci/hda/hda_sysfs.c

@@ -221,7 +221,7 @@ static ssize_t init_verbs_show(struct device *dev,
 	mutex_lock(&codec->user_mutex);
 	for (i = 0; i < codec->init_verbs.used; i++) {
 		struct hda_verb *v = snd_array_elem(&codec->init_verbs, i);
-		len += snprintf(buf + len, PAGE_SIZE - len,
+		len += scnprintf(buf + len, PAGE_SIZE - len,
 				"0x%02x 0x%03x 0x%04x\n",
 				v->nid, v->verb, v->param);
 	}
@@ -271,7 +271,7 @@ static ssize_t hints_show(struct device *dev,
 	mutex_lock(&codec->user_mutex);
 	for (i = 0; i < codec->hints.used; i++) {
 		struct hda_hint *hint = snd_array_elem(&codec->hints, i);
-		len += snprintf(buf + len, PAGE_SIZE - len,
+		len += scnprintf(buf + len, PAGE_SIZE - len,
 				"%s = %s\n", hint->key, hint->val);
 	}
 	mutex_unlock(&codec->user_mutex);