Fix Coverity defects (#8579)

Fix Coverity CID355287 and CID355289: technically it is a false-positive but it is easier to put a pattern in the code that they can recognise as a sanitizer. The compiler will remove it during optimization. Fix CID353973: the security condition is unlikely to occur but we can avoid it completely. Fix resource leak from CID 355286 and CID 355288. Fixing new resource leak introduced by a previous commit (CID355449)

2 files changed, 39 insertions, 0 deletions

diff --git a/libnetdata/libnetdata.c b/libnetdata/libnetdata.c
index 70b656d838..c9b7ab1983 100644
--- a/libnetdata/libnetdata.c
+++ b/libnetdata/libnetdata.c
@@ -1453,3 +1453,41 @@ void recursive_config_double_dir_load(const char *user_path, const char *stock_p
     freez(udir);
     freez(sdir);
 }
+
+// Returns the number of bytes read from the file if file_size is not NULL.
+// The actual buffer has an extra byte set to zero (not included in the count).
+char *read_by_filename(char *filename, long *file_size)
+{
+    FILE *f = fopen(filename, "r");
+    if (!f)
+        return NULL;
+    if (fseek(f, 0, SEEK_END) < 0) {
+        fclose(f);
+        return NULL;
+    }
+    long size = ftell(f);
+    if (size <= 0 || fseek(f, 0, SEEK_END) < 0) {
+        fclose(f);
+        return NULL;
+    }
+    char *contents = callocz(size + 1, 1);
+    if (!contents) {
+        fclose(f);
+        return NULL;
+    }
+    if (fseek(f, 0, SEEK_SET) < 0) {
+        fclose(f);
+        freez(contents);
+        return NULL;
+    }
+    size_t res = fread(contents, 1, size, f);
+    if ( res != (size_t)size) {
+        freez(contents);
+        fclose(f);
+        return NULL;
+    }
+    fclose(f);
+    if (file_size)
+        *file_size = size;
+    return contents;
+}
diff --git a/libnetdata/libnetdata.h b/libnetdata/libnetdata.h
index b7fa9d5aba..45ac6e81bf 100644
--- a/libnetdata/libnetdata.h
+++ b/libnetdata/libnetdata.h
@@ -278,6 +278,7 @@ extern void recursive_config_double_dir_load(
         , void *data
         , size_t depth
 );
+extern char *read_by_filename(char *filename, long *file_size);
 
 /* fix for alpine linux */
 #ifndef RUSAGE_THREAD