xfs: 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().

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_stats.c

@@ -57,13 +57,13 @@ int xfs_stats_format(struct xfsstats __percpu *stats, char *buf)
 	/* Loop over all stats groups */
 
 	for (i = j = 0; i < ARRAY_SIZE(xstats); i++) {
-		len += snprintf(buf + len, PATH_MAX - len, "%s",
+		len += scnprintf(buf + len, PATH_MAX - len, "%s",
 				xstats[i].desc);
 		/* inner loop does each group */
 		for (; j < xstats[i].endpoint; j++)
-			len += snprintf(buf + len, PATH_MAX - len, " %u",
+			len += scnprintf(buf + len, PATH_MAX - len, " %u",
 					counter_val(stats, j));
-		len += snprintf(buf + len, PATH_MAX - len, "\n");
+		len += scnprintf(buf + len, PATH_MAX - len, "\n");
 	}
 	/* extra precision counters */
 	for_each_possible_cpu(i) {
@@ -72,9 +72,9 @@ int xfs_stats_format(struct xfsstats __percpu *stats, char *buf)
 		xs_read_bytes += per_cpu_ptr(stats, i)->s.xs_read_bytes;
 	}
 
-	len += snprintf(buf + len, PATH_MAX-len, "xpc %Lu %Lu %Lu\n",
+	len += scnprintf(buf + len, PATH_MAX-len, "xpc %Lu %Lu %Lu\n",
 			xs_xstrat_bytes, xs_write_bytes, xs_read_bytes);
-	len += snprintf(buf + len, PATH_MAX-len, "debug %u\n",
+	len += scnprintf(buf + len, PATH_MAX-len, "debug %u\n",
 #if defined(DEBUG)
 		1);
 #else