[Webkit-unassigned] [Bug 202150] New: [JSC] Null dereference in propagateTransitions

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=202150

            Bug ID: 202150
           Summary: [JSC] Null dereference in propagateTransitions
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: antoniogroza at gmail.com

Hello, 
While fuzzing JSC i have found a test case that is able to reproduce the following issue: https://bugs.webkit.org/show_bug.cgi?id=200983 .

function hax() {
for (const v3 in "AAAAAAAAAAA") {
    const v4 = createGlobalObject();
    with (v4) {
        v4.b = parseInt;
        v4.length = v3;
        const v6 = new Uint16Array();
    }
}
}

hax();

Execute it on an ASAN build of JSC with the following options to repro: 

./jsc --useConcurrentJIT=false --useConcurrentGC=false --thresholdForJITSoon=10 --thresholdForJITAfterWarmUp=10 --thresholdForOptimizeAfterWarmUp=100 --thresholdForOptimizeAfterLongWarmUp=100 --thresholdForOptimizeAfterLongWarmUp=100 --thresholdForFTLOptimizeAfterWarmUp=1000 --thresholdForFTLOptimizeSoon=1000 --gcAtEnd=true poc.js

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