[wpe-webkit] Bug within QML based webbrowsers

[Marco Felsch]

On 20-06-03 15:06, Marco Felsch wrote:
> Hi all,
> 
> this is my first time posting to this list and I'm very new to the
> webkit project too. Currently I debug a memory issue and need some help.
> 
> The current sw-stack:
>  - QT 5.12.6
>  - Webkit 2.28.2
>  - libwpe 1.6.0
>  - wpebackend-fdo 1.6.0
> 
> The error pattern:
> I get a white (empty) picture when I try to start the QML demo from the
> Tools/MiniBrowser/wpe/qt/. This pattern will appear with the wayland and
> the eglfs qt backend.
> 
> I've debugged this a few days and my findings are:
> The code is loooping around trying to find the correct memory to
> free within Source/bmalloc/bmalloc/Map.h:94. Freeing the memory
> happens due to the string-table re-allocation which happens during
> the ResourceResponseBase::ResourceResponseBase() call.

Sorry, I mean the string re-allocation happens during handling the
Messages::WebPageProxy::DecidePolicyForResponse
(Source/WebKit/UIProcess/ProvisionalPageProxy.cpp:441).

Regards,
  Marco

> I debugged it
> using the gdb and saw that the 'oldTable' which should be freed
> (Source/WTF/wtf/HashTable.h:1358) using a key which doesn't exist yet.
> 
> The bug occured with the update from:
>  - Webkit 2.26.3 -> 2.28.2
>  - libwpe 1.4.0.1 -> 1.6.0
>  - wpebackend-fdo 1.4.1 -> 1.6.0.
> The bug isn't triggered if I run the cog browser or the Minibrowser from
> Tools/MiniBrowser/wpe. We switched to the system-allocator as workaround
> since our target is a 32-Bit ARMv7 Cortex-A9 which can't use the
> gigacage security mechanism anyway.
> 
> Thanks for your answers =)
> 
> Regards,
>   Marco
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