From 3b7fe9237b740c85f8654d231dd243c3eb94033b Mon Sep 17 00:00:00 2001
From: Daniel Danzberger <daniel@dd-wrt.com>
Date: Tue, 9 Jun 2020 22:24:58 +0200
Subject: [PATCH] dm_strword: fix invalid memory access

Calling this dm_strword with an emtpy 'str' can cause invalid memory
access. This commit checks for an empty string.

NOTE: This function is insecure and can cause segfaults
      when 'str' is larger than 'source'

Signed-off-by: Daniel Danzberger <daniel@dd-wrt.com>
---
 libbbf_api/dmcommon.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libbbf_api/dmcommon.c b/libbbf_api/dmcommon.c
index 6a7ba611..81fc2cb3 100644
--- a/libbbf_api/dmcommon.c
+++ b/libbbf_api/dmcommon.c
@@ -1137,8 +1137,10 @@ static inline int isword_delim(char c)
 char *dm_strword(char *src, char *str)
 {
 	char *ret = src;
-	if (src[0] == '\0')
+
+	if (src[0] == 0 || str[0] == 0)
 		return NULL;
+
 	int len = strlen(str);
 	while ((ret = strstr(ret, str)) != NULL) {
 		if ((ret == src && isword_delim(ret[len])) ||