Add parse depth limit to FormCalc parser

Due to the recursive nature of the FormCalc parser, deeply nested
expressions can lead to memory being exhausted. This check is being
added to have the parser exit early instead of running out of
memory. This should reduce the number of false positives about
addressing issues being found by fuzzers.

BUG=chromium:752433

Change-Id: I511ecfb07e32073555e1fd1658f3b8b47f1a5a91
Reviewed-on: https://pdfium-review.googlesource.com/11170
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp b/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp
index 9907890e83..214fd4aec3 100644
--- a/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp
+++ b/xfa/fxfa/fm2js/cxfa_fmparser_unittest.cpp
@@ -107,3 +107,10 @@ TEST(CXFA_FMParserTest, Parse) {
   EXPECT_TRUE(ast->ToJavaScript(buf));
   EXPECT_EQ(ret, buf.AsStringC());
 }
+
+TEST(CXFA_FMParserTest, MaxParseDepth) {
+  auto parser = pdfium::MakeUnique<CXFA_FMParser>(L"foo(bar[baz(fizz[0])])");
+  parser->SetMaxParseDepthForTest(5);
+  EXPECT_EQ(nullptr, parser->Parse());
+  EXPECT_TRUE(parser->HasError());
+}