dynamic_debug: fix ddebug_parse_query()

This fixes following scenario:

  $ echo 'file dynamic_debug.c line 1-123 +p' > /sys/kernel/debug/dynamic_debug/control
  -bash: echo: write error: Invalid argument
  $ dmesg | grep dynamic_debug
  dynamic_debug:ddebug_parse_query: last-line:123 < 1st-line:1
  dynamic_debug:ddebug_parse_query: query parse failed
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Jason Baron <jbaron@akamai.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/dynamic_debug.c

@@ -352,8 +352,10 @@ static int ddebug_parse_query(char *words[], int nwords,
 				return -EINVAL;
 			if (last) {
 				/* range <first>-<last> */
-				if (parse_lineno(last, &query->last_lineno)
-				    < query->first_lineno) {
+				if (parse_lineno(last, &query->last_lineno) < 0)
+					return -EINVAL;
+
+				if (query->last_lineno < query->first_lineno) {
 					pr_err("last-line:%d < 1st-line:%d\n",
 						query->last_lineno,
 						query->first_lineno);