Fix CVE-2020-12762.

This commit is a squashed backport of the following commits
on the master branch:

  * 099016b7e8
  * 77d935b7ae
  * d07b910149
  * 519dfe1591
  * a59d5acfab
  * 26f080997d

arraylist.c

@@ -136,6 +136,9 @@ int array_list_del_idx(struct array_list *arr, size_t idx, size_t count)
 {
 	size_t i, stop;
 
+	/* Avoid overflow in calculation with large indices. */
+	if (idx > SIZE_T_MAX - count)
+		return -1;
 	stop = idx + count;
 	if (idx >= arr->length || stop > arr->length)
 		return -1;

linkhash.c

@@ -12,6 +12,7 @@
 
 #include "config.h"
 
+#include <assert.h>
 #include <limits.h>
 #include <stdarg.h>
 #include <stddef.h>
@@ -499,6 +500,8 @@ struct lh_table *lh_table_new(int size, lh_entry_free_fn *free_fn, lh_hash_fn *h
 	int i;
 	struct lh_table *t;
 
+	/* Allocate space for elements to avoid divisions by zero. */
+	assert(size > 0);
 	t = (struct lh_table *)calloc(1, sizeof(struct lh_table));
 	if (!t)
 		return NULL;
@@ -578,8 +581,12 @@ int lh_table_insert_w_hash(struct lh_table *t, const void *k, const void *v, con
 	unsigned long n;
 
 	if (t->count >= t->size * LH_LOAD_FACTOR)
-		if (lh_table_resize(t, t->size * 2) != 0)
+	{
+		/* Avoid signed integer overflow with large tables. */
+		int new_size = (t->size > INT_MAX / 2) ? INT_MAX : (t->size * 2);
+		if (t->size == INT_MAX || lh_table_resize(t, new_size) != 0)
 			return -1;
+	}
 
 	n = h % t->size;
 

printbuf.c

@@ -15,6 +15,7 @@
 
 #include "config.h"
 
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -66,9 +67,16 @@ static int printbuf_extend(struct printbuf *p, int min_size)
 	if (p->size >= min_size)
 		return 0;
 
-	new_size = p->size * 2;
-	if (new_size < min_size + 8)
+	/* Prevent signed integer overflows with large buffers. */
+	if (min_size > INT_MAX - 8)
+		return -1;
+	if (p->size > INT_MAX / 2)
 		new_size = min_size + 8;
+	else {
+		new_size = p->size * 2;
+		if (new_size < min_size + 8)
+			new_size = min_size + 8;
+	}
 #ifdef PRINTBUF_DEBUG
 	MC_DEBUG("printbuf_memappend: realloc "
 	         "bpos=%d min_size=%d old_size=%d new_size=%d\n",
@@ -83,6 +91,9 @@ static int printbuf_extend(struct printbuf *p, int min_size)
 
 int printbuf_memappend(struct printbuf *p, const char *buf, int size)
 {
+	/* Prevent signed integer overflows with large buffers. */
+	if (size > INT_MAX - p->bpos - 1)
+		return -1;
 	if (p->size <= p->bpos + size + 1)
 	{
 		if (printbuf_extend(p, p->bpos + size + 1) < 0)
@@ -100,6 +111,9 @@ int printbuf_memset(struct printbuf *pb, int offset, int charvalue, int len)
 
 	if (offset == -1)
 		offset = pb->bpos;
+	/* Prevent signed integer overflows with large buffers. */
+	if (len > INT_MAX - offset)
+		return -1;
 	size_needed = offset + len;
 	if (pb->size < size_needed)
 	{

tests/test4.c

@@ -3,12 +3,15 @@
  */
 
 #include "config.h"
+#include <assert.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "json_inttypes.h"
 #include "json_object.h"
 #include "json_tokener.h"
+#include "snprintf_compat.h"
 
 void print_hex(const char *s)
 {
@@ -24,6 +27,29 @@ void print_hex(const char *s)
 	putchar('\n');
 }
 
+static void test_lot_of_adds(void);
+static void test_lot_of_adds()
+{
+	int ii;
+	char key[50];
+	json_object *jobj = json_object_new_object();
+	assert(jobj != NULL);
+	for (ii = 0; ii < 500; ii++)
+	{
+		snprintf(key, sizeof(key), "k%d", ii);
+		json_object *iobj = json_object_new_int(ii);
+		assert(iobj != NULL);
+		if (json_object_object_add(jobj, key, iobj))
+		{
+			fprintf(stderr, "FAILED to add object #%d\n", ii);
+			abort();
+		}
+	}
+	printf("%s\n", json_object_to_json_string(jobj));
+	assert(json_object_object_length(jobj) == 500);
+	json_object_put(jobj);
+}
+
 int main(void)
 {
 	const char *input = "\"\\ud840\\udd26,\\ud840\\udd27,\\ud800\\udd26,\\ud800\\udd27\"";
@@ -52,5 +78,8 @@ int main(void)
 		retval = 1;
 	}
 	json_object_put(parse_result);
+
+	test_lot_of_adds();
+
 	return retval;
 }