1678442 - Assertion failure: (data_ & TagMask) == Tag, at vm/JSScript.h:1263

Status: VERIFIED FIXED

(Core :: JavaScript Engine, defect)

Description

[Christian Holler (:decoder)]

The following testcase crashes on mozilla-central revision 20201118-9d797387f57c (debug build, run with --fuzzing-safe --cpu-count=2 --ion-offthread-compile=off):

function y() {}
function x() {}
Reflect.construct(x, [y.toSource.toSource],
 Object.defineProperty(function(){}.bind(), "prototype", {
  get() {
    relazifyFunctions()
  }
}));

Backtrace:

received signal SIGSEGV, Segmentation fault.
0x0000555557961cd9 in js::jit::MaybeEnterJit(JSContext*, js::RunState&) ()
#0  0x0000555557961cd9 in js::jit::MaybeEnterJit(JSContext*, js::RunState&) ()
#1  0x0000555556b8f19e in Interpret(JSContext*, js::RunState&) ()
#2  0x0000555556b85b68 in js::RunScript(JSContext*, js::RunState&) ()
#3  0x0000555556b9c513 in js::ExecuteKernel(JSContext*, JS::Handle<JSScript*>, JS::Handle<JSObject*>, JS::Handle<JS::Value>, js::AbstractFramePtr, JS::MutableHandle<JS::Value>) ()
#4  0x0000555556b9cc2d in js::Execute(JSContext*, JS::Handle<JSScript*>, JS::Handle<JSObject*>, JS::MutableHandle<JS::Value>) ()
#5  0x0000555556d4e615 in ExecuteScript(JSContext*, JS::Handle<JSObject*>, JS::Handle<JSScript*>, JS::MutableHandle<JS::Value>) ()
#6  0x0000555556d4e7f2 in JS_ExecuteScript(JSContext*, JS::Handle<JSScript*>) ()
#7  0x0000555556a68ef7 in RunFile(JSContext*, char const*, _IO_FILE*, CompileUtf8, bool) ()
#8  0x0000555556a685d9 in Process(JSContext*, char const*, bool, FileKind) ()
#9  0x0000555556a0a86f in Shell(JSContext*, js::cli::OptionParser*, char**) ()
#10 0x0000555556a02e1c in main ()
rax	0x55555574cd92	93824994299282
rbx	0x7ffff6024000	140737320730624
rcx	0x555557fe0ea8	93825036848808
rdx	0x0	0
rsi	0x7ffff7105770	140737338431344
rdi	0x7ffff7104540	140737338426688
rbp	0x7fffffffbb60	140737488337760
rsp	0x7fffffffb820	140737488336928
r8	0x7ffff7105770	140737338431344
r9	0x7ffff7f998c0	140737353717952
r10	0x58	88
r11	0x7ffff6dac7a0	140737334921120
r12	0x2	2
r13	0x1e893109a0b0	33574582067376
r14	0x3ce3bbede670	66948808173168
r15	0x7fffffffc000	140737488338944
rip	0x555557961cd9 <js::jit::MaybeEnterJit(JSContext*, js::RunState&)+2601>
=> 0x555557961cd9 <_ZN2js3jit13MaybeEnterJitEP9JSContextRNS_8RunStateE+2601>:	movl   $0x4ef,0x0
   0x555557961ce4 <_ZN2js3jit13MaybeEnterJitEP9JSContextRNS_8RunStateE+2612>:	callq  0x555556a923a6 <abort>

Not sure about the implications of this but the assertion doesn't look good, so marking s-s until triaged.

Comment 1

[Christian Holler (:decoder)]

Attachment: Testcase

Comment 2

[Jason Kratzer [:jkratzer]]

Bugmon Analysis:
Verified bug as reproducible on mozilla-central 20201119214432-b703fa5c3d16.
The bug appears to have been introduced in the following build range:

Start: 17ecebdc6d8b5b4b8fb4e20392f6380928207a14 (20201116134131)
End: cb856cdf7a0c46c463dac3fbf57c81d55afff66e (20201116140333)
Pushlog: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=17ecebdc6d8b5b4b8fb4e20392f6380928207a14&tochange=cb856cdf7a0c46c463dac3fbf57c81d55afff66e

Comment 3

[Jan de Mooij [:jandem]]

Looking into this..

Comment 4

[Jan de Mooij [:jandem]]

This is limited to the relazifyFunctions testing function. Normally we don't allow relazifying in active compartments, but relazifyFunctions lifts that restriction for testing, triggering the bug here.

Comment 5

[Jan de Mooij [:jandem]]

Attachment: Bug 1678442 part 1 - Use stronger assertion in JSFunction::nonLazyScript. r?tcampbell!

Comment 6

[Jan de Mooij [:jandem]]

Attachment: Bug 1678442 part 2 - Guard against this-creation relazifying the callee. r?tcampbell!

TI code used to delazify as part of this-creation and removing that code exposed this.
It's only an issue when the testing function is used and only affects the C++
interpreter.

Drive-by change: remove some dead code in CacheIR.cpp

Depends on D97744

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/827e5e9015f9
part 1 - Use stronger assertion in JSFunction::nonLazyScript. r=tcampbell
https://hg.mozilla.org/integration/autoland/rev/bb1d6e149c11
part 2 - Guard against this-creation relazifying the callee. r=tcampbell

Comment 8

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/827e5e9015f9
https://hg.mozilla.org/mozilla-central/rev/bb1d6e149c11

Comment 9

[Jason Kratzer [:jkratzer]]

Bugmon Analysis:
Verified bug as fixed on rev mozilla-central 20201130215246-d9b010547747.
Removing bugmon keyword as no further action possible.
Please review the bug and re-add the keyword for further analysis.