Bug 222542 – Crash calling the "load" function on a too large file in the jsc command line tool

• Component: JavaScriptCore
• Status: NEW

[Xiaoyu He]

Created attachment 421808 [details]
poc

0x7ffff4681fab <raise+187>      mov    edi, 0x2
   0x7ffff4681fb0 <raise+192>      mov    eax, 0xe
   0x7ffff4681fb5 <raise+197>      syscall 
 → 0x7ffff4681fb7 <raise+199>      mov    rcx, QWORD PTR [rsp+0x108]
   0x7ffff4681fbf <raise+207>      xor    rcx, QWORD PTR fs:0x28
   0x7ffff4681fc8 <raise+216>      mov    eax, r8d
   0x7ffff4681fcb <raise+219>      jne    0x7ffff4681fec <__GI_raise+252>
   0x7ffff4681fcd <raise+221>      add    rsp, 0x118
   0x7ffff4681fd4 <raise+228>      ret    
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── threads ────
[#0] Id 1, Name: "jsc_afl_asan18", stopped, reason: SIGABRT
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── trace ────
[#0] 0x7ffff4681fb7 → __GI_raise(sig=0x6)
[#1] 0x7ffff4683921 → __GI_abort()
[#2] 0x59c516 → allocateBuffer<WTF::FailureAction::Crash>()
[#3] 0x5ef736 → reserveCapacity<WTF::FailureAction::Crash>()
[#4] 0x5ef3e3 → expandCapacity<WTF::FailureAction::Crash>()
[#5] 0x5eec66 → resize()
[#6] 0x5851ab → fillBufferWithContentsOfFile<WTF::Vector<char, 0, WTF::CrashOnOverflow, 16, WTF::FastMalloc> >()
[#7] 0x5851ab → fillBufferWithContentsOfFile()
[#8] 0x5851ab → fetchScriptFromLocalFileSystem()
[#9] 0x54378d → functionLoad()

[Radar WebKit Bug Importer]

<rdar://problem/74863969>

[Darin Adler]

This intentional crash is a policy of the "jsc" command line tool, not of JavaScriptCore itself. Could easily be changed, but is not a JavaScriptCore security bug.

[Darin Adler]

Trivial to fix by adding a tryReserveCapacity call to the fillBufferWithContentsOfFile function.

[Xiaoyu He]

Can you give me a CVE number?

[Darin Adler]

I don’t think this is a security bug since it’s specific to the "jsc" command line tool. It interferes with fuzzing, but has no effect on security of web browsers using JavaScriptCore, for example.

[Yusuke Suzuki]

Yes. This is not a security issue since it always crashes and it only exists in JSC shell (this is not included in WebContent process).