When !HAVE(BACKTRACE) && !OS(WINDOWS), - WTFGetBacktrace(samples, &frames) make frames = 0 - WTFReportBacktraceWithPrefixAndPrintStream passes -2 (=frames-framesToSkip) to WTFPrintBacktraceWithPrefixAndPrintStream. - WTFPrintBacktraceWithPrefixAndPrintStream static_cast -2 to size_t, which can overflow and make large number. - It possibly tries to print the large stack and eventually crashes. void WTFReportBacktraceWithPrefixAndPrintStream(PrintStream& out, const char* prefix) { static constexpr int framesToShow = 31; static constexpr int framesToSkip = 2; void* samples[framesToShow + framesToSkip]; int frames = framesToShow + framesToSkip; WTFGetBacktrace(samples, &frames); WTFPrintBacktraceWithPrefixAndPrintStream(out, samples + framesToSkip, frames - framesToSkip, prefix); } https://github.com/WebKit/WebKit/blob/f33e99829e4f572a15eb8c2a6ca3d78fa227e9cc/Source/WTF/wtf/Assertions.cpp#L298-L307 void WTFGetBacktrace(void** stack, int* size) { #if HAVE(BACKTRACE) *size = backtrace(stack, *size); #elif OS(WINDOWS) *size = RtlCaptureStackBackTrace(0, *size, stack, nullptr); #else UNUSED_PARAM(stack); *size = 0; #endif } https://github.com/WebKit/WebKit/blob/f33e99829e4f572a15eb8c2a6ca3d78fa227e9cc/Source/WTF/wtf/StackTrace.cpp#L34-L44 void WTFPrintBacktraceWithPrefixAndPrintStream(PrintStream& out, void** stack, int size, const char* prefix) { out.print(StackTracePrinter { { stack, static_cast<size_t>(size) }, prefix }); } https://github.com/WebKit/WebKit/blob/f33e99829e4f572a15eb8c2a6ca3d78fa227e9cc/Source/WTF/wtf/Assertions.cpp#L309-L312
Note: WTF::StackTrace::captureStackTrace has similar code, but it blocks the code by "static_cast<size_t>(capturedFrames) > framesToSkip". std::unique_ptr<StackTrace> StackTrace::captureStackTrace(size_t maxFrames, size_t framesToSkip) { static_assert(sizeof(StackTrace) == sizeof(void*) * 3); // We overwrite the memory of the two first skipped frames, m_stack[0] will hold the third one. static_assert(offsetof(StackTrace, m_stack) == sizeof(void*) * 2); maxFrames = std::max<size_t>(1, maxFrames); // Skip 2 additional frames i.e. StackTrace::captureStackTrace and WTFGetBacktrace. framesToSkip += 2; size_t capacity = maxFrames + framesToSkip; void** storage = static_cast<void**>(fastMalloc(capacity * sizeof(void*))); size_t size = 0; size_t initialFrame = 0; int capturedFrames = static_cast<int>(capacity); WTFGetBacktrace(storage, &capturedFrames); if (static_cast<size_t>(capturedFrames) > framesToSkip) { size = static_cast<size_t>(capturedFrames) - framesToSkip; initialFrame = framesToSkip - 2; } return std::unique_ptr<StackTrace> { new (NotNull, storage) StackTrace(size, initialFrame) }; } https://github.com/WebKit/WebKit/blob/f33e99829e4f572a15eb8c2a6ca3d78fa227e9cc/Source/WTF/wtf/StackTrace.cpp#L48-L68
Pull request: https://github.com/WebKit/WebKit/pull/17726
Committed 268121@main (a4279526dfa5): <https://commits.webkit.org/268121@main> Reviewed commits have been landed. Closing PR #17726 and removing active labels.
<rdar://problem/115721690>