asan/ubsan builers are reporting undefined behavior in vm_host_tools

https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8930572229835117984


https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8930579471445424112

vm_host_tools-0.0.1-r200:  * ASAN error detected:
vm_host_tools-0.0.1-r200:  * ../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/vm_tools/concierge/subnet_test.cc:76:3: runtime error: shift exponent 32 is too large for 32-bit type 'unsigned int'
vm_host_tools-0.0.1-r200:  *     #0 0x7fbd0b946a98 in vm_tools::concierge::PrefixTest_Netmask_Test::TestBody() /build/amd64-generic/var/cache/portage/chromeos-base/vm_host_tools/out/Default/../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/vm_tools/concierge/subnet_test.cc:76:3
vm_host_tools-0.0.1-r200:  *     #1 0x7fbd0b7f8e83 in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2402:10
vm_host_tools-0.0.1-r200:  *     #2 0x7fbd0b7f8e83 in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2438:0
vm_host_tools-0.0.1-r200:  *     #3 0x7fbd0b7df520 in testing::Test::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2474:5
vm_host_tools-0.0.1-r200:  *     #4 0x7fbd0b7e047f in testing::TestInfo::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2656:11
vm_host_tools-0.0.1-r200:  *     #5 0x7fbd0b7e0b06 in testing::TestCase::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2774:28
vm_host_tools-0.0.1-r200:  *     #6 0x7fbd0b7e96c6 in testing::internal::UnitTestImpl::RunAllTests() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:4649:43
vm_host_tools-0.0.1-r200:  *     #7 0x7fbd0b7f99a3 in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2402:10
vm_host_tools-0.0.1-r200:  *     #8 0x7fbd0b7f99a3 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2438:0
vm_host_tools-0.0.1-r200:  *     #9 0x7fbd0b7e928c in testing::UnitTest::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:4257:10
vm_host_tools-0.0.1-r200:  *     #10 0x7fbd0b9e8375 in RUN_ALL_TESTS() /build/amd64-generic/var/cache/portage/chromeos-base/vm_host_tools/out/Default/../../../../../../../usr/include/gtest/gtest.h:2233:46
vm_host_tools-0.0.1-r200:  *     #11 0x7fbd0b9e8375 in main /build/amd64-generic/var/cache/portage/chromeos-base/vm_host_tools/out/Default/../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/common-mk/testrunner.cc:16:0
vm_host_tools-0.0.1-r200:  *     #12 0x7fbd092f3735 in __libc_start_main /var/tmp/portage/cross-x86_64-cros-linux-gnu/glibc-2.23-r21/work/glibc-2.23/csu/../csu/libc-start.c:289:0
vm_host_tools-0.0.1-r200:  *     #13 0x7fbd0b84f708 in _start ??:0:0
vm_host_tools-0.0.1-r200:  * 
vm_host_tools-0.0.1-r200:  * SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/vm_tools/concierge/subnet_test.cc:76:3 in
vm_host_tools-0.0.1-r200:  * ../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/vm_tools/concierge/subnet.cc:42:10: runtime error: shift exponent 32 is too large for 32-bit type 'unsigned int'
vm_host_tools-0.0.1-r200:  *     #0 0x7fbd0b9cae17 in vm_tools::concierge::Subnet::Netmask() const /build/amd64-generic/var/cache/portage/chromeos-base/vm_host_tools/out/Default/../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/vm_tools/concierge/subnet.cc:42:10
vm_host_tools-0.0.1-r200:  *     #1 0x7fbd0b9467c2 in vm_tools::concierge::PrefixTest_Netmask_Test::TestBody() /build/amd64-generic/var/cache/portage/chromeos-base/vm_host_tools/out/Default/../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/vm_tools/concierge/subnet_test.cc:76:3
vm_host_tools-0.0.1-r200:  *     #2 0x7fbd0b7f8e83 in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2402:10
vm_host_tools-0.0.1-r200:  *     #3 0x7fbd0b7f8e83 in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2438:0
vm_host_tools-0.0.1-r200:  *     #4 0x7fbd0b7df520 in testing::Test::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2474:5
vm_host_tools-0.0.1-r200:  *     #5 0x7fbd0b7e047f in testing::TestInfo::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2656:11
vm_host_tools-0.0.1-r200:  *     #6 0x7fbd0b7e0b06 in testing::TestCase::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2774:28
vm_host_tools-0.0.1-r200:  *     #7 0x7fbd0b7e96c6 in testing::internal::UnitTestImpl::RunAllTests() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:4649:43
vm_host_tools-0.0.1-r200:  *     #8 0x7fbd0b7f99a3 in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2402:10
vm_host_tools-0.0.1-r200:  *     #9 0x7fbd0b7f99a3 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:2438:0
vm_host_tools-0.0.1-r200:  *     #10 0x7fbd0b7e928c in testing::UnitTest::Run() /build/amd64-generic/tmp/portage/dev-cpp/gtest-1.8.0-r1/work/googletest-release-1.8.0/googletest-abi_x86_64.amd64/./src/gtest.cc:4257:10
vm_host_tools-0.0.1-r200:  *     #11 0x7fbd0b9e8375 in RUN_ALL_TESTS() /build/amd64-generic/var/cache/portage/chromeos-base/vm_host_tools/out/Default/../../../../../../../usr/include/gtest/gtest.h:2233:46
vm_host_tools-0.0.1-r200:  *     #12 0x7fbd0b9e8375 in main /build/amd64-generic/var/cache/portage/chromeos-base/vm_host_tools/out/Default/../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/common-mk/testrunner.cc:16:0
vm_host_tools-0.0.1-r200:  *     #13 0x7fbd092f3735 in __libc_start_main /var/tmp/portage/cross-x86_64-cros-linux-gnu/glibc-2.23-r21/work/glibc-2.23/csu/../csu/libc-start.c:289:0
vm_host_tools-0.0.1-r200:  *     #14 0x7fbd0b84f708 in _start ??:0:0
vm_host_tools-0.0.1-r200:  * 
vm_host_tools-0.0.1-r200:  * SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../../../../../../../tmp/portage/chromeos-base/vm_host_tools-0.0.1-r200/work/vm_host_tools-0.0.1/vm_tools/concierge/subnet.cc:42:10 in
vm_host_tools-0.0.1-r200: