Assertion failure: false, at /home/worker/workspace/build/src/media/libstagefright/binding/include/mp4_demuxer/ByteReader.h:129 Found with mozilla-central asan debug buildID=20170327212148 Looks like this could possibly trigger an invalid read, marking s-s ==59547==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f72293c7a8a bp 0x7f71f49f6b30 sp 0x7f71f49f6b30 T55) ==59547==The signal is caused by a WRITE memory access. ==59547==Hint: address points to the zero page. #0 0x7f72293c7a89 in mp4_demuxer::ByteReader::ReadU32() /home/worker/workspace/build/src/media/libstagefright/binding/include/mp4_demuxer/ByteReader.h:129:7 #1 0x7f72293e96a7 in mp4_demuxer::Edts::Edts(mp4_demuxer::Box&) /home/worker/workspace/build/src/media/libstagefright/binding/MoofParser.cpp:836:34 #2 0x7f72293e3992 in mp4_demuxer::MoofParser::ParseTrak(mp4_demuxer::Box&) /home/worker/workspace/build/src/media/libstagefright/binding/MoofParser.cpp:271:15 #3 0x7f72293e1f4d in mp4_demuxer::MoofParser::ParseMoov(mp4_demuxer::Box&) /home/worker/workspace/build/src/media/libstagefright/binding/MoofParser.cpp:251:7 #4 0x7f72293e172c in mp4_demuxer::MoofParser::RebuildFragmentedIndex(mp4_demuxer::BoxContext&) /home/worker/workspace/build/src/media/libstagefright/binding/MoofParser.cpp:50:7 #5 0x7f72293d70c3 in mp4_demuxer::MoofParser::RebuildFragmentedIndex(mozilla::media::IntervalSet<long> const&) /home/worker/workspace/build/src/media/libstagefright/binding/MoofParser.cpp:38:10 #6 0x7f722db4a95b in mozilla::MP4TrackDemuxer::EnsureUpToDateIndex() /home/worker/workspace/build/src/dom/media/fmp4/MP4Demuxer.cpp:322:11 #7 0x7f722db4a1fd in mozilla::MP4TrackDemuxer::MP4TrackDemuxer(mozilla::MP4Demuxer*, mozilla::UniquePtr<mozilla::TrackInfo, mozilla::DefaultDelete<mozilla::TrackInfo> >&&, mp4_demuxer::IndiceWrapper const&) /home/worker/workspace/build/src/dom/media/fmp4/MP4Demuxer.cpp:279:3 #8 0x7f722db48fe6 in mozilla::MP4Demuxer::Init() /home/worker/workspace/build/src/dom/media/fmp4/MP4Demuxer.cpp:173:35 #9 0x7f722d6ce1a5 in mozilla::MediaFormatReader::DemuxerProxy::Init()::$_10::operator()() const /home/worker/workspace/build/src/dom/media/MediaFormatReader.cpp:1008:47 ... see log.txt

It's just a `MOZ_ASSERT(false)`, which does `*((volatile int*) NULL) = line;` (i.e., writing the line number at 0x0) in debug builds to force a crash. So this is not a sec issue. The problem is in MoofParser.cpp:836, reader->ReadU32() probably goes too far. The test at line 821 above may be incorrect, or we need another kind of check here.

We should probably just remove the assertion from ByteReader.

(:kentuckyfriedtakahe, :k17e) from comment #3) > We should probably just remove the assertion from ByteReader. Looks like bug 1387793 took care of that.