replace: count_strstr - Handle an edge case where sub is empty

If sub is empty, avoids an infinite loop.

function                                             old     new   delta
count_strstr                                          45      63     +18

Signed-off-by: Martin Lewis <martin.lewis.x84@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/libbb/replace.c b/libbb/replace.c
index a661d96e6..6183d3e6f 100644
--- a/libbb/replace.c
+++ b/libbb/replace.c
@@ -15,6 +15,10 @@ unsigned FAST_FUNC count_strstr(const char *str, const char *sub)
         size_t sub_len = strlen(sub);
         unsigned count = 0;
 
+        /* If sub is empty, avoid an infinite loop */
+        if (sub_len == 0)
+                return strlen(str) + 1;
+
         while ((str = strstr(str, sub)) != NULL) {
                 count++;
                 str += sub_len;