Found while fuzzing mozilla-central rev e67bca14d669 (built with: --enable-debug --enable-fuzzing).

Unfortunately I don't have a reliable testcase at the moment but will update this if one becomes available.

Assertion failure: mSentFinishOrAbort, at /dom/indexedDB/IDBFileHandle.cpp:65

    ==20487==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f588dc24c5a bp 0x7ffff8c99bf0 sp 0x7ffff8c99bd0 T20487)
    ==20487==The signal is caused by a WRITE memory access.
    ==20487==Hint: address points to the zero page.
        #0 0x7f588dc24c5a in mozilla::dom::IDBFileHandle::~IDBFileHandle() /dom/indexedDB/IDBFileHandle.cpp:65:3
        #1 0x7f588dc24e90 in mozilla::dom::IDBFileHandle::~IDBFileHandle() /dom/indexedDB/IDBFileHandle.cpp:61:33
        #2 0x7f58899ea228 in SnowWhiteKiller::MaybeKillObject(SnowWhiteKiller::SnowWhiteObject&) /xpcom/base/nsCycleCollector.cpp:2426:29
        #3 0x7f58899df346 in SnowWhiteKiller::~SnowWhiteKiller() /xpcom/base/nsCycleCollector.cpp:2413:7
        #4 0x7f58899dea9a in nsCycleCollector::FreeSnowWhite(bool) /xpcom/base/nsCycleCollector.cpp:2603:3
        #5 0x7f58899e2e32 in nsCycleCollector::BeginCollection(ccType, nsICycleCollectorListener*) /xpcom/base/nsCycleCollector.cpp:3583:3
        #6 0x7f58899e2a09 in nsCycleCollector::Collect(ccType, js::SliceBudget&, nsICycleCollectorListener*, bool) /xpcom/base/nsCycleCollector.cpp:3407:9
        #7 0x7f58899e27a7 in nsCycleCollector::ShutdownCollect() /xpcom/base/nsCycleCollector.cpp:3350:20
        #8 0x7f58899e39d6 in nsCycleCollector::Shutdown(bool) /xpcom/base/nsCycleCollector.cpp:3644:5
        #9 0x7f58899e5412 in nsCycleCollector_shutdown(bool) /xpcom/base/nsCycleCollector.cpp:3959:18
        #10 0x7f5889b0b3be in mozilla::ShutdownXPCOM(nsIServiceManager*) /xpcom/build/XPCOMInit.cpp:709:3
        #11 0x7f588fbb40ac in XRE_TermEmbedding() /toolkit/xre/nsEmbedFunctions.cpp:218:3
        #12 0x7f588a41a15e in mozilla::ipc::ScopedXREEmbed::Stop() /ipc/glue/ScopedXREEmbed.cpp:90:5
        #13 0x7f588fbb4697 in XRE_InitChildProcess(int, char**, XREChildData const*) /toolkit/xre/nsEmbedFunctions.cpp:753:16
        #14 0x5643ef8ccab6 in content_process_main /browser/app/../../ipc/contentproc/plugin-container.cpp:57:28
        #15 0x5643ef8ccab6 in main /browser/app/nsBrowserApp.cpp:327:18
        #16 0x7f589f9250b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
        #17 0x5643ef8a98bc in _start (/home/worker/builds/m-c-20210814094200-fuzzing-debug/firefox-bin+0x158bc)
    
    UndefinedBehaviorSanitizer can not provide additional info.
    SUMMARY: UndefinedBehaviorSanitizer: SEGV /dom/indexedDB/IDBFileHandle.cpp:65:3 in mozilla::dom::IDBFileHandle::~IDBFileHandle()
    ==20487==ABORTING

Hi Jason, were you lucky to find a reliable test case here?

Jens, sorry for the slow response. Unfortunately I still haven't managed to find a testcase reliable enough to include here. Nor have I been able to get a pernosco session for this issue. However this issue is still occurring regularly. The last crash was found on 2021-10-01.

The IDBFileHandle has gone.