resolve: fix NULL deref on strv comparison

A strv might be NULL if it is empty. The txt.strings comparison doesn't
take that into account. Introduce strv_equal() to provide a proper helper
for this and fix resolve to use it.

Thanks to Stanisław Pitucha <viraptor@gmail.com> for reporting this!

2 files changed, 13 insertions, 0 deletions

diff --git a/src/shared/strv.c b/src/shared/strv.c
index aeb93eac6b..a5f8a2aff6 100644
--- a/src/shared/strv.c
+++ b/src/shared/strv.c
@@ -587,6 +587,17 @@ char **strv_sort(char **l) {
         return l;
 }
 
+bool strv_equal(char **a, char **b) {
+        if (!a || !b)
+                return a == b;
+
+        for ( ; *a || *b; ++a, ++b)
+                if (!streq_ptr(*a, *b))
+                        return false;
+
+        return true;
+}
+
 void strv_print(char **l) {
         char **s;
 
diff --git a/src/shared/strv.h b/src/shared/strv.h
index 47618bd26c..774c67a8c8 100644
--- a/src/shared/strv.h
+++ b/src/shared/strv.h
@@ -49,6 +49,8 @@ int strv_consume_prepend(char ***l, char *value);
 char **strv_remove(char **l, const char *s);
 char **strv_uniq(char **l);
 
+bool strv_equal(char **a, char **b);
+
 #define strv_contains(l, s) (!!strv_find((l), (s)))
 
 char **strv_new(const char *x, ...) _sentinel_;