Bug 142160 – ASSERTION FAILED: charactersWritten > 0 && static_cast<unsigned>(charactersWritten) < sizeof(buffer) in JSC::dateProtoFuncToISOString

• Component: JavaScriptCore
• Status: RESOLVED WORKSFORME

[Renata Hodovan]

Created attachment 247657 [details]
Test case

Load this script with debug jsc:

var d = new Date(0);
d.setUTCFullYear(-200e6);
d.toISOString();


Backtrace:

ASSERTION FAILED: charactersWritten > 0 && static_cast<unsigned>(charactersWritten) < sizeof(buffer)
../../Source/JavaScriptCore/runtime/DatePrototype.cpp(542) : JSC::EncodedJSValue JSC::dateProtoFuncToISOString(JSC::ExecState*)
1   0x7ffff73f24ca /home/reni/data/REPOS/webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18(WTFCrash+0x1e) [0x7ffff73f24ca]
2   0x7ffff724a1c9 /home/reni/data/REPOS/webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18(_ZN3JSC24dateProtoFuncToISOStringEPNS_9ExecStateE+0x410) [0x7ffff724a1c9]
3   0x7fffadfff0a8 [0x7fffadfff0a8]

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff73f24cf in WTFCrash () at ../../Source/WTF/wtf/Assertions.cpp:321
321	    *(int *)(uintptr_t)0xbbadbeef = 0;
(gdb) bt
#0  0x00007ffff73f24cf in WTFCrash () at ../../Source/WTF/wtf/Assertions.cpp:321
#1  0x00007ffff724a1c9 in JSC::dateProtoFuncToISOString (exec=0x7fffffffca90) at ../../Source/JavaScriptCore/runtime/DatePrototype.cpp:542
#2  0x00007fffadfff0a8 in ?? ()
#3  0x00007fffffffcad0 in ?? ()
#4  0x00007ffff73a05ef in llint_entry () from /home/reni/data/REPOS/webkit/WebKitBuild/Debug/lib/libjavascriptcoregtk-4.0.so.18

[Alexey Proskuryakov]

Which part of the assertion condition is untrue? That's sort of a big difference.

[Renata Hodovan]

(In reply to comment #1)
> Which part of the assertion condition is untrue? That's sort of a big
> difference.

The second part of the condition fails, since 30 characters was written but the size if the buffer is only 28. (However, this case is handled in the next line so we don't end up in a crash in release.)

[Alexey Proskuryakov]

I see, it's an snprintf, and we have a check later, so no buffer overrun.

[Renata Hodovan]

Cannot repro this anymore.