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Commit 0f625061 authored Nov 02, 2021 by Yi-Yo Chiang

libfiemap: array boundary check for fiemap.fm_extents[]

Ensure we have at least one element before we try to access the last
element. Else the array index of the last element may underflow,
0ull - 1 == ~0ull == UINT64_MAX.

Bug: 204536075
Test: atest fiemap_writer_test
Change-Id: Ic390d108bf789cfe136fb5dfe2983f3c7d6f7e48

parent cab12f8a

fs_mgr/libfiemap/fiemap_writer.cpp

+4 −0

Original line number	Diff line number	Diff line
		@@ -514,6 +514,10 @@ static bool IsLastExtent(const fiemap_extent* extent) {
		static bool FiemapToExtents(struct fiemap* fiemap, std::vector<struct fiemap_extent>* extents,
		std::string_view file_path) {
		uint32_t num_extents = fiemap->fm_mapped_extents;
		if (num_extents == 0) {
		LOG(ERROR) << "File " << file_path << " has zero extent";
		return false;
		}
		const struct fiemap_extent* last_extent = &fiemap->fm_extents[num_extents - 1];
		if (!IsLastExtent(last_extent)) {
		LOG(ERROR) << "FIEMAP did not return a final extent for file: " << file_path

fs_mgr/libfiemap/fiemap_writer_test.cpp

+7 −0

Original line number	Diff line number	Diff line
		@@ -258,6 +258,13 @@ TEST_F(FiemapWriterTest, FibmapBlockAddressing) {
		EXPECT_EQ(memcmp(actual.data(), data.data(), data.size()), 0);
		}

		TEST_F(FiemapWriterTest, CheckEmptyFile) {
		// Can't get any fiemap_extent out of a zero-sized file.
		FiemapUniquePtr fptr = FiemapWriter::Open(testfile, 0);
		EXPECT_EQ(fptr, nullptr);
		EXPECT_EQ(access(testfile.c_str(), F_OK), -1);
		}

		TEST_F(SplitFiemapTest, Create) {
		auto ptr = SplitFiemap::Create(testfile, 1024 * 768, 1024 * 32);
		ASSERT_NE(ptr, nullptr);