Bug 299529 – [GStreamer] _gst_util_uint64_scale_int: assertion "num >= 0" failed

• Status: RESOLVED
• Resolution: FIXED
• Component: Media

[Michael Catanzaro]

I saw this fatal-criticals crash when viewing an image on imgur.com using Epiphany Tech Preview with WebKitGTK 2.50.0. Unfortunately I was unable to figure out how to reproduce it.

#0  _g_log_abort (breakpoint=<optimized out>) at ../glib/gmessages.c:430
#1  g_logv
    (log_domain=0x7f2a054b49f7 "GStreamer", log_level=G_LOG_LEVEL_CRITICAL, format=<optimized out>, args=args@entry=0x7ffe78245e90) at ../glib/gmessages.c:1291
#2  0x00007f2a0470f7e3 in g_log
    (log_domain=log_domain@entry=0x7f2a054b49f7 "GStreamer", log_level=log_level@entry=G_LOG_LEVEL_CRITICAL, format=format@entry=0x7f2a0476e360 "%s: assertion '%s' failed") at ../glib/gmessages.c:1333
#3  0x00007f2a0471016d in g_return_if_fail_warning
    (log_domain=log_domain@entry=0x7f2a054b49f7 "GStreamer", pretty_function=pretty_function@entry=0x7f2a054e44b0 <__func__.59> "_gst_util_uint64_scale_int", expression=expression@entry=0x7f2a054c0401 "num >= 0")
    at ../glib/gmessages.c:3162
#4  0x00007f2a0548f6b2 in _gst_util_uint64_scale_int
    (val=<optimized out>, num=<optimized out>, denom=<optimized out>, correct=0) at ../gst/gstutils.c:726
#5  gst_util_uint64_scale_int (val=<optimized out>, num=<optimized out>, denom=<optimized out>)
    at ../gst/gstutils.c:775
#6  0x00007f2a0c3bbbe8 in WebCore::MediaPlayerPrivateGStreamer::updateVideoSizeAndOrientationFromCaps
    (this=0x7f290e32a070, caps=<optimized out>)
    at /usr/lib/debug/source/sdk/webkitgtk-6.0.bst/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:3785
#7  0x00007f2a0c3c6420 in WebCore::MediaPlayerPrivateGStreamer::triggerRepaint(WTF::GRefPtr<_GstSample, WTF::GRefPtrDefaultRefDerefTraits<_GstSample> >&&)::$_0::operator()() const (this=<optimized out>)
    at /usr/lib/debug/source/sdk/webkitgtk-6.0.bst/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:3881
#8  WTF::Detail::CallableWrapper<WebCore::MediaPlayerPrivateGStreamer::triggerRepaint(WTF::GRefPtr<_GstSample, WTF::GRefPtrDefaultRefDerefTraits<_GstSample> >&&)::$_0, void>::call (this=<optimized out>)
    at WTF/Headers/wtf/Function.h:53
#9  0x00007f2a08a823a5 in WTF::Function<void()>::operator() (this=0x7ffe78246070)
    at /usr/lib/debug/source/sdk/webkitgtk-6.0.bst/Source/WTF/wtf/Function.h:82
#10 WTF::RunLoop::performWork (this=0x7f29e7008180)
    at /usr/lib/debug/source/sdk/webkitgtk-6.0.bst/Source/WTF/wtf/RunLoop.cpp:148

Full backtrace is attached.

[Michael Catanzaro]

Created attachment 476855 [details]
Full backtrace

[Philippe Normand]

#6  0x00007f2a0c3bbbe8 in WebCore::MediaPlayerPrivateGStreamer::updateVideoSizeAndOrientationFromCaps (this=0x7f290e32a070, caps=<optimized out>) at /usr/lib/debug/source/sdk/webkitgtk-6.0.bst/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:3785
        pixelAspectRatioNumerator = 7201628
        pixelAspectRatioDenominator = 7170075
        stride = 0
        frameRate = 30
        format = GST_VIDEO_FORMAT_DMA_DRM
        colorSpace = {primaries = std::optional = {[contained value] = WebCore::PlatformVideoColorPrimaries::Bt709}, transfer = std::optional = {[contained value] = WebCore::PlatformVideoTransferCharacteristics::Bt709}, matrix = std::optional = {[contained value] = WebCore::PlatformVideoMatrixCoefficients::Bt709}, fullRange = std::optional = {[contained value] = false}}
        pad = {m_ptr = 0x559009ac6430 [GstGhostPad|sink]}
        tagsEvent = {m_ptr = 0x7f270400c790 [GstEvent]}
        orientation = <optimized out>
        originalSize = {m_width = 330, m_height = <optimized out>}
        scopeExit = {m_exitFunction = {this = 0x7f290e32a070}, m_executeOnDestruction = true}
        displayWidth = -479607514
        displayHeight = 351333675
        displayAspectRatioGCD = <optimized out>
        width = 0
        height = 0

Well the negative displayWidth is clearly suspicious :) Too bad the m_height originalSize isn't reported... Maybe a unit-test could be written using these values.

[Cristina Murillo]

The calculation for the displayWidth overflows. The displayWidth is a signed integer calculated by multiplying the width with the pixel-aspect-ratio numerator. 
The pixelAspectRatioNumerator in the trace is 7201628, causing an overflow and therefore, the negative value in the display width.
The negative value is passed to the function _gst_util_uint64_scale_int, causing the assertion.

[Cristina Murillo]

Pull request: https://github.com/WebKit/WebKit/pull/52302

[EWS]

Committed 301767@main (2a29f6f8ced1): <https://commits.webkit.org/301767@main>

Reviewed commits have been landed. Closing PR #52302 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/162923071>