hashtable: fix environment variable corruption

Only first previously deleted entry was recognized, leading hsearch_r
to think that there was no previously deleted entry. It then conluded
that a free entry was found, even if there were no free entries and it
overwrote a random entry.

This patch makes sure all deleted or free entries are always found and
also introduces constants for the 0 and -1 numbers. Unit tests to excersise a
simple hash table usage and catch the corruption were added.

To trash your environment, simply run this loop:

setenv i 0
while true; do
    setenv v_$i $i
    setenv v_$i
    setexpr i $i + 1
done

Signed-off-by: Roman Kapl <rka@sysgo.com>

2 files changed, 126 insertions, 0 deletions

diff --git a/test/env/Makefile b/test/env/Makefile
index d71a11b..5c8eae3 100644
--- a/test/env/Makefile
+++ b/test/env/Makefile
@@ -4,3 +4,4 @@
 
 obj-y += cmd_ut_env.o
 obj-y += attr.o
+obj-y += hashtable.o
diff --git a/test/env/hashtable.c b/test/env/hashtable.c
new file mode 100644
index 0000000..8c87e65
--- /dev/null
+++ b/test/env/hashtable.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * (C) Copyright 2019
+ * Roman Kapl, SYSGO, rka@sysgo.com
+ */
+
+#include <common.h>
+#include <command.h>
+#include <search.h>
+#include <stdio.h>
+#include <test/env.h>
+#include <test/ut.h>
+
+#define SIZE 32
+#define ITERATIONS 10000
+
+static int htab_fill(struct unit_test_state *uts,
+		     struct hsearch_data *htab, size_t size)
+{
+	size_t i;
+	ENTRY item;
+	ENTRY *ritem;
+	char key[20];
+
+	for (i = 0; i < size; i++) {
+		sprintf(key, "%d", (int)i);
+		item.callback = NULL;
+		item.data = key;
+		item.flags = 0;
+		item.key = key;
+		ut_asserteq(1, hsearch_r(item, ENTER, &ritem, htab, 0));
+	}
+
+	return 0;
+}
+
+static int htab_check_fill(struct unit_test_state *uts,
+			   struct hsearch_data *htab, size_t size)
+{
+	size_t i;
+	ENTRY item;
+	ENTRY *ritem;
+	char key[20];
+
+	for (i = 0; i < size; i++) {
+		sprintf(key, "%d", (int)i);
+		item.callback = NULL;
+		item.flags = 0;
+		item.data = key;
+		item.key = key;
+		hsearch_r(item, FIND, &ritem, htab, 0);
+		ut_assert(ritem);
+		ut_asserteq_str(key, ritem->key);
+		ut_asserteq_str(key, ritem->data);
+	}
+
+	return 0;
+}
+
+static int htab_create_delete(struct unit_test_state *uts,
+			      struct hsearch_data *htab, size_t iterations)
+{
+	size_t i;
+	ENTRY item;
+	ENTRY *ritem;
+	char key[20];
+
+	for (i = 0; i < iterations; i++) {
+		sprintf(key, "cd-%d", (int)i);
+		item.callback = NULL;
+		item.flags = 0;
+		item.data = key;
+		item.key = key;
+		hsearch_r(item, ENTER, &ritem, htab, 0);
+		ritem = NULL;
+
+		hsearch_r(item, FIND, &ritem, htab, 0);
+		ut_assert(ritem);
+		ut_asserteq_str(key, ritem->key);
+		ut_asserteq_str(key, ritem->data);
+
+		ut_asserteq(1, hdelete_r(key, htab, 0));
+	}
+
+	return 0;
+}
+
+/* Completely fill up the hash table */
+static int env_test_htab_fill(struct unit_test_state *uts)
+{
+	struct hsearch_data htab;
+
+	memset(&htab, 0, sizeof(htab));
+	ut_asserteq(1, hcreate_r(SIZE, &htab));
+
+	ut_assertok(htab_fill(uts, &htab, SIZE));
+	ut_assertok(htab_check_fill(uts, &htab, SIZE));
+	ut_asserteq(SIZE, htab.filled);
+
+	hdestroy_r(&htab);
+	return 0;
+}
+
+ENV_TEST(env_test_htab_fill, 0);
+
+/* Fill the hashtable up halfway an repeateadly delete/create elements
+ * and check for corruption
+ */
+static int env_test_htab_deletes(struct unit_test_state *uts)
+{
+	struct hsearch_data htab;
+
+	memset(&htab, 0, sizeof(htab));
+	ut_asserteq(1, hcreate_r(SIZE, &htab));
+
+	ut_assertok(htab_fill(uts, &htab, SIZE / 2));
+	ut_assertok(htab_create_delete(uts, &htab, ITERATIONS));
+	ut_assertok(htab_check_fill(uts, &htab, SIZE / 2));
+	ut_asserteq(SIZE / 2, htab.filled);
+
+	hdestroy_r(&htab);
+	return 0;
+}
+
+ENV_TEST(env_test_htab_deletes, 0);