Crash when clearing std::optional<WebKit::WebServiceWorkerFetchTaskClient::BlobLoader>

[youenn fablet]

==79588==ERROR: AddressSanitizer: heap-use-after-free on address 0x60700015ad90 at pc 0x00010b45eb67 bp 0x7ffee743cb50 sp 0x7ffee743cb48
WRITE of size 1 at 0x60700015ad90 thread T0
==79588==WARNING: invalid path to external symbolizer!
==79588==WARNING: Failed to use and restart external symbolizer!
#0 0x10b45eb66 in std::optional<WebKit::WebServiceWorkerFetchTaskClient::BlobLoader>::clear() (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0xcf0b66)
#1 0x10b45d0ed in std::optional<WebKit::WebServiceWorkerFetchTaskClient::BlobLoader>::operator=(std::nullopt_t) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0xcef0ed)
#2 0x11cc2b119 in WebCore::DocumentThreadableLoader::didFinishLoading(unsigned long) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebCore.framework/Versions/A/WebCore:x86_64+0x28f6119)
#3 0x11cd42967 in WebCore::CachedResource::checkNotify() (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebCore.framework/Versions/A/WebCore:x86_64+0x2a0d967)
#4 0x11cd3f6ba in WebCore::CachedRawResource::finishLoading(WebCore::SharedBuffer*) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebCore.framework/Versions/A/WebCore:x86_64+0x2a0a6ba)
#5 0x11ccddc2e in WebCore::SubresourceLoader::didFinishLoading(WebCore::NetworkLoadMetrics const&) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebCore.framework/Versions/A/WebCore:x86_64+0x29a8c2e)
#6 0x10b42382b in WebKit::WebResourceLoader::didFinishResourceLoad(WebCore::NetworkLoadMetrics const&) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0xcb582b)
#7 0x10b426b8e in void IPC::handleMessage<Messages::WebResourceLoader::DidFinishResourceLoad, WebKit::WebResourceLoader, void (WebKit::WebResourceLoader::*)(WebCore::NetworkLoadMetrics const&)>(IPC::Decoder&, WebKit::WebResourceLoader*, void (WebKit::WebResourceLoader::*)(WebCore::NetworkLoadMetrics const&)) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0xcb8b8e)
#8 0x10b42607f in WebKit::WebResourceLoader::didReceiveWebResourceLoaderMessage(IPC::Connection&, IPC::Decoder&) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0xcb807f)
#9 0x10aaf07c0 in WebKit::NetworkProcessConnection::didReceiveMessage(IPC::Connection&, IPC::Decoder&) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0x3827c0)
#10 0x10a8a496e in IPC::Connection::dispatchMessage(std::__1::unique_ptr<IPC::Decoder, std::__1::default_delete<IPC::Decoder> >) (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0x13696e)
#11 0x10a8ae486 in IPC::Connection::dispatchOneMessage() (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/WebKit.framework/Versions/A/WebKit:x86_64+0x140486)
#12 0x12b2321a7 in WTF::RunLoop::performWork() (/Volumes/Data/slave/high-sierra-asan-release-wk2-tests/build/buildToTest/JavaScriptCore.framework/Versions/A/JavaScrip<br> (Truncated recent description)

[youenn fablet]

Created attachment 329960 [details]
Patch

[Alex Christensen]

Comment on attachment 329960 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=329960&action=review

> Source/WebKit/WebProcess/Storage/WebServiceWorkerFetchTaskClient.cpp:117
> -    m_blobLoader = std::nullopt;
> +    auto toDelete = WTFMove(m_blobLoader);

I think it would be better to just do std::exchange(m_blobLoader, std::nullopt).  Then we wouldn't need to give anything a strange unused name.

[youenn fablet]

Created attachment 329966 [details]
Patch for landing

[WebKit Commit Bot]

Comment on attachment 329966 [details]
Patch for landing

Clearing flags on attachment: 329966

Committed r226206: <https://trac.webkit.org/changeset/226206>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/36168892>