SUMMARY In order to determine whether the wallpaper is animated or not, MediaProxy::determineBackgroundType uses the following algorithm: if (QMovie::supportedFormats().contains(QFileInfo(filePath).suffix().toLower().toLatin1())) { This enumerates all image types that support animations, then checks whether the one we care about is contained in the list. Unfortunately, to check which image types support animations, QMovie::supportedFormats() needs to instantiate each and every image reader plugin that is available and ask it whether it supports animations. STEPS TO REPRODUCE We have caught this in Fedora by accident, because we ran into a bug: https://bugzilla.redhat.com/show_bug.cgi?id=2144200 where Chromium and PDFium would fail to load on Apple hardware using "Apple Silicon" ARM CPUs. This surprisingly lead to the whole Plasma shell failing to start because the QImage PDF reader would crash during initialization, crashing the entire shell along with it. Since image reader plugins can generally be of varying quality, it would be much safer to avoid instantiating less tested exotic plugins when we do not actually need them. OBSERVED RESULT A crash in PDFium can crash the entire Plasma Shell, turning QtPdf into a critical package. EXPECTED RESULT The Plasma Shell should not load PDFium unless the wallpaper is actually a PDF. And likewise for other rarely used image decoding plugins. SOFTWARE/OS VERSIONS All current Plasma versions, on all hardware. The crash can be reproduced by using an unfixed QtWebEngine/QtPdf on Apple Silicon hardware, but the underlying issue exists everywhere. ADDITIONAL INFORMATION Instead of enumerating all image formats that support animation using QMovie::supportedFormats(): if (QMovie::supportedFormats().contains(QFileInfo(filePath).suffix().toLower().toLatin1())) { the better way would be to do what QMovie::supportedFormats() does internally, but only on the type we actually care about, without enumerating them: QBuffer dummyBuffer; dummyBuffer.open(QIODevice::ReadOnly); if (QImageReader(&dummyBuffer, QFileInfo(filePath).suffix().toLower().toLatin1()).supportsOption(QImageIOHandler::Animation)) { See also the downstream bug report: https://bugzilla.redhat.com/show_bug.cgi?id=2144200#c22
A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-workspace/-/merge_requests/2374
Git commit 2f743037d132a4cf611e20604032ec7002c99b8b by Fushan Wen. Committed on 28/11/2022 at 00:22. Pushed by fusionfuture into branch 'master'. Do not query all available image plugins when determining background type In order to determine whether the wallpaper is animated or not, MediaProxy::determineBackgroundType uses the following algorithm: if (QMovie::supportedFormats().contains(QFileInfo(filePath).suffix().toLower().toLatin1())) { This enumerates all image types that support animations, then checks whether the one we care about is contained in the list. Unfortunately, to check which image types support animations, QMovie::supportedFormats() needs to instantiate each and every image reader plugin that is available and ask it whether it supports animations. STEPS TO REPRODUCE We have caught this in Fedora by accident, because we ran into a bug: https://bugzilla.redhat.com/show_bug.cgi?id=2144200 where Chromium and PDFium would fail to load on Apple hardware using "Apple Silicon" ARM CPUs. This surprisingly lead to the whole Plasma shell failing to start because the QImage PDF reader would crash during initialization, crashing the entire shell along with it. Since image reader plugins can generally be of varying quality, it would be much safer to avoid instantiating less tested exotic plugins when we do not actually need them. A crash in PDFium can crash the entire Plasma Shell, turning QtPdf into a critical package. Instead of enumerating all image formats that support animation using QMovie::supportedFormats(), the better way would be to do what QMovie::supportedFormats() does internally, but only on the type we actually care about, without enumerating them. See also the downstream bug report: https://bugzilla.redhat.com/show_bug.cgi?id=2144200#c22 Co-authored-by: Kevin Kofler <kevin.kofler@chello.at> FIXED-IN: 5.26.4 M +7 -1 wallpapers/image/plugin/utils/mediaproxy.cpp https://invent.kde.org/plasma/plasma-workspace/commit/2f743037d132a4cf611e20604032ec7002c99b8b
Git commit fe738f146f7a1ffafb4d242ac130760b97f2ef32 by Fushan Wen. Committed on 28/11/2022 at 02:34. Pushed by fusionfuture into branch 'cherry-pick-2f743037'. Do not query all available image plugins when determining background type In order to determine whether the wallpaper is animated or not, MediaProxy::determineBackgroundType uses the following algorithm: if (QMovie::supportedFormats().contains(QFileInfo(filePath).suffix().toLower().toLatin1())) { This enumerates all image types that support animations, then checks whether the one we care about is contained in the list. Unfortunately, to check which image types support animations, QMovie::supportedFormats() needs to instantiate each and every image reader plugin that is available and ask it whether it supports animations. STEPS TO REPRODUCE We have caught this in Fedora by accident, because we ran into a bug: https://bugzilla.redhat.com/show_bug.cgi?id=2144200 where Chromium and PDFium would fail to load on Apple hardware using "Apple Silicon" ARM CPUs. This surprisingly lead to the whole Plasma shell failing to start because the QImage PDF reader would crash during initialization, crashing the entire shell along with it. Since image reader plugins can generally be of varying quality, it would be much safer to avoid instantiating less tested exotic plugins when we do not actually need them. A crash in PDFium can crash the entire Plasma Shell, turning QtPdf into a critical package. Instead of enumerating all image formats that support animation using QMovie::supportedFormats(), the better way would be to do what QMovie::supportedFormats() does internally, but only on the type we actually care about, without enumerating them. See also the downstream bug report: https://bugzilla.redhat.com/show_bug.cgi?id=2144200#c22 Co-authored-by: Kevin Kofler <kevin.kofler@chello.at> FIXED-IN: 5.26.4 (cherry picked from commit 2f743037d132a4cf611e20604032ec7002c99b8b) M +7 -1 wallpapers/image/plugin/utils/mediaproxy.cpp https://invent.kde.org/plasma/plasma-workspace/commit/fe738f146f7a1ffafb4d242ac130760b97f2ef32