tty: nozomi: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit. Fix it by replacing with scnprintf().

Also rewrite the code in a standard if-form instead of ugly
conditional operators.

Signed-off-by: Takashi Iwai <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/nozomi.c

···
 	static char buf[TMP_BUF_MAX];
 	char *p = buf;
 
-	interrupt & MDM_DL1 ? p += snprintf(p, TMP_BUF_MAX, "MDM_DL1 ") : NULL;
-	interrupt & MDM_DL2 ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"MDM_DL2 ") : NULL;
+	if (interrupt & MDM_DL1)
+		p += scnprintf(p, TMP_BUF_MAX, "MDM_DL1 ");
+	if (interrupt & MDM_DL2)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "MDM_DL2 ");
+	if (interrupt & MDM_UL1)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "MDM_UL1 ");
+	if (interrupt & MDM_UL2)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "MDM_UL2 ");
+	if (interrupt & DIAG_DL1)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "DIAG_DL1 ");
+	if (interrupt & DIAG_DL2)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "DIAG_DL2 ");
 
-	interrupt & MDM_UL1 ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"MDM_UL1 ") : NULL;
-	interrupt & MDM_UL2 ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"MDM_UL2 ") : NULL;
+	if (interrupt & DIAG_UL)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "DIAG_UL ");
 
-	interrupt & DIAG_DL1 ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"DIAG_DL1 ") : NULL;
-	interrupt & DIAG_DL2 ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"DIAG_DL2 ") : NULL;
+	if (interrupt & APP1_DL)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "APP1_DL ");
+	if (interrupt & APP2_DL)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "APP2_DL ");
 
-	interrupt & DIAG_UL ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"DIAG_UL ") : NULL;
+	if (interrupt & APP1_UL)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "APP1_UL ");
+	if (interrupt & APP2_UL)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "APP2_UL ");
 
-	interrupt & APP1_DL ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"APP1_DL ") : NULL;
-	interrupt & APP2_DL ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"APP2_DL ") : NULL;
+	if (interrupt & CTRL_DL)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "CTRL_DL ");
+	if (interrupt & CTRL_UL)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "CTRL_UL ");
 
-	interrupt & APP1_UL ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"APP1_UL ") : NULL;
-	interrupt & APP2_UL ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"APP2_UL ") : NULL;
-
-	interrupt & CTRL_DL ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"CTRL_DL ") : NULL;
-	interrupt & CTRL_UL ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"CTRL_UL ") : NULL;
-
-	interrupt & RESET ? p += snprintf(p, TMP_BUF_MAX - (p - buf),
-					"RESET ") : NULL;
+	if (interrupt & RESET)
+		p += scnprintf(p, TMP_BUF_MAX - (p - buf), "RESET ");
 
 	return buf;
 }