Bug 171801 – Null pointer dereference in WTF::RefPtr<WTF::StringImpl>::operator!() under slow_path_get_direct_pname

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Kamil Frankowicz]

Created attachment 309352 [details]
POC to trigger null pointer dereference (jsc)

Affected SVN revision: 216356

To reproduce the problem:
./jsc jsc_null_ptr_ref_ptr.js

ASAN Output:

==21363==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f1a0150fc49 bp 0x7ffec7ffda30 sp 0x7ffec7ffd7c0 T0)
==21363==The signal is caused by a READ memory access.
==21363==Hint: address points to the zero page.
    #0 0x7f1a0150fc48 in WTF::RefPtr<WTF::StringImpl>::operator!() const /XYZ/WebKit/Source/WTF/wtf/RefPtr.h:76:38
    #1 0x7f1a0150fc48 in WTF::String::isNull() const /XYZ/WebKit/Source/WTF/wtf/text/WTFString.h:150
    #2 0x7f1a0150fc48 in JSC::JSString::isRope() const /XYZ/WebKit/Source/JavaScriptCore/runtime/JSString.h:208
    #3 0x7f1a0150fc48 in JSC::JSString::toAtomicString(JSC::ExecState*) const /XYZ/WebKit/Source/JavaScriptCore/runtime/JSString.h:529
    #4 0x7f1a0150fc48 in JSC::JSString::toIdentifier(JSC::ExecState*) const /XYZ/WebKit/Source/JavaScriptCore/runtime/JSString.h:524
    #5 0x7f1a0150fc48 in slow_path_get_direct_pname /XYZ/WebKit/Source/JavaScriptCore/runtime/CommonSlowPaths.cpp:732
    #6 0x7f1a00ce76d9  (/XYZ/WebKit/WebKitBuild/Release/lib/libJavaScriptCore.so.1+0x2b9f6d9)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /XYZ/WebKit/Source/WTF/wtf/RefPtr.h:76:38 in WTF::RefPtr<WTF::StringImpl>::operator!() const
==21363==ABORTING

[Radar WebKit Bug Importer]

<rdar://problem/32066936>

[Filip Pizlo]

Created attachment 309611 [details]
the patch

[Michael Saboff]

Comment on attachment 309611 [details]
the patch

r=me

[Filip Pizlo]

Landed in https://trac.webkit.org/changeset/216593/webkit