libfdt: tests: add get_next_tag_invalid_prop_len

Add a new test get_next_tag_invalid_prop_len, which covers
fdt_next_tag(), when it is passed an corrupted blob, with
invalid property len values. The test runs twice, on a blob
in sw and finished state.

Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Message-Id: <20221011182611.116011-2-tadeusz.struk@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

tests/.gitignore

@@ -74,3 +74,4 @@ tmp.*
 /truncated_memrsv
 /utilfdt_test
 /value-labels
+/get_next_tag_invalid_prop_len

tests/Makefile.tests

@@ -4,7 +4,7 @@ LIB_TESTS_L = get_mem_rsv \
 	get_path supernode_atdepth_offset parent_offset \
 	node_offset_by_prop_value node_offset_by_phandle \
 	node_check_compatible node_offset_by_compatible \
-	get_alias \
+	get_alias get_next_tag_invalid_prop_len \
 	char_literal \
 	sized_cells \
 	notfound \

tests/get_next_tag_invalid_prop_len.c

@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+/*
+ * libfdt - Flat Device Tree manipulation
+ *	Testcase for fdt_next_tag()
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <libfdt.h>
+#include "tests.h"
+#include "testdata.h"
+
+#define FDT_SIZE 65536
+#define CHECK_ERR(err) \
+({ if (err) \
+	FAIL("%s: %d: %s", __FILE__, __LINE__, fdt_strerror(err)); \
+})
+
+static void fdt_next_tag_test(bool fdt_finished)
+{
+	struct fdt_property *prp;
+	void *fdt;
+	int nextoff = 0, offset, err;
+	uint32_t tag;
+
+	fdt = malloc(FDT_SIZE);
+	if (!fdt)
+		FAIL("Can't allocate memory");
+	err = fdt_create(fdt, FDT_SIZE);
+	CHECK_ERR(err);
+	err = fdt_finish_reservemap(fdt);
+	CHECK_ERR(err);
+	/* Create a root node and add two properties */
+	err = fdt_begin_node(fdt, "");
+	CHECK_ERR(err);
+	err = fdt_property_u32(fdt, "prop-int-32", 0x1234);
+	CHECK_ERR(err);
+	err = fdt_property_u32(fdt, "prop2-int-32", 0x4321);
+	CHECK_ERR(err);
+	err = fdt_end_node(fdt);
+	CHECK_ERR(err);
+	if (fdt_finished) {
+		/* Call fdt_finish to set the correct fdt state. */
+		err = fdt_finish(fdt);
+		CHECK_ERR(err);
+	}
+
+	offset = fdt_first_property_offset(fdt, 0);
+	if (offset <= 0)
+		FAIL("Invalid offset %x, expected value greater than 0, finished=%d\n",
+		     offset, fdt_finished);
+
+	/* Normal case */
+	tag = fdt_next_tag(fdt, offset, &nextoff);
+	if (tag != FDT_PROP)
+		FAIL("Invalid tag %x, expected FDT_PROP, finished=%d\n",
+		     tag, fdt_finished);
+	if (nextoff <= 0)
+		FAIL("Invalid nextoff %d, expected value greater than 0, finished=%d",
+		     nextoff, fdt_finished);
+
+	/* Get a writable ptr to the first property and corrupt the length */
+	prp = fdt_get_property_by_offset_w(fdt, offset, NULL);
+	if (!prp)
+		FAIL("Bad property pointer, finished=%d", fdt_finished);
+
+	/* int overflow case */
+	prp->len = cpu_to_fdt32(0xFFFFFFFA);
+	tag = fdt_next_tag(fdt, offset, &nextoff);
+	if (tag != FDT_END)
+		FAIL("Invalid tag %x, expected premature FDT_END, finished=%d",
+		     tag, fdt_finished);
+	if (nextoff != -FDT_ERR_BADSTRUCTURE)
+		FAIL("Invalid nextoff, expected error -FDT_ERR_BADSTRUCTURE, finished=%d",
+		     fdt_finished);
+
+	/* negative offset case */
+	prp->len = cpu_to_fdt32(0x7FFFFFFA);
+	tag = fdt_next_tag(fdt, offset, &nextoff);
+	if (tag != FDT_END)
+		FAIL("Invalid tag %x, expected premature FDT_END, finished=%d",
+		     tag, fdt_finished);
+	if (nextoff != -FDT_ERR_BADSTRUCTURE)
+		FAIL("Invalid nextoff, expected -FDT_ERR_BADSTRUCTURE, finished=%d",
+		     fdt_finished);
+
+	free(fdt);
+}
+
+int main(int argc, char *argv[])
+{
+	test_init(argc, argv);
+
+	fdt_next_tag_test(false);
+	fdt_next_tag_test(true);
+
+	PASS();
+}

tests/meson.build

@@ -47,6 +47,7 @@ tests = [
   'get_path',
   'get_phandle',
   'get_prop_offset',
+  'get_next_tag_invalid_prop_len',
   'getprop',
   'incbin',
   'integer-expressions',

tests/run_tests.sh

@@ -513,6 +513,7 @@ libfdt_tests () {
     run_dtc_test -I fs -O dts -o fs.test_tree1.test.dts $FSBASE/test_tree1
     run_dtc_test -I fs -O dtb -o fs.test_tree1.test.dtb $FSBASE/test_tree1
     run_test dtbs_equal_unordered -m fs.test_tree1.test.dtb test_tree1.dtb
+    run_test get_next_tag_invalid_prop_len
 
     ## https://github.com/dgibson/dtc/issues/64
     check_tests "$SRCDIR/phandle-args-overflow.dts" clocks_property