738279 - crash in firebug-debugger after stepping over an bad object reference

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Attila Soki]

Attachment: testcase-1

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:11.0) Gecko/20100101 Firefox/11.0
Build ID: 20120312181643

Steps to reproduce:

Debugged the attached testcase-1.

1. open Firebug, enable the script tab and load the attached testcase-1
2. debugger stops at breakpoint (A), (reload the site if the debugger don't stops)
3. click step over
4. now the cursor is at line (B), click step over again
5. now, hover the sourcecode in the firebug window at the bottom
6. crash

Firefox 11.0 + Firebug 1.9.1
Firefox nightly 14.0a1 (2012-03-22) + Firebug 10.0.a5

Crash ID: bp-1de8762a-de1f-4850-976d-afc0e2120322



Actual results:

crash


Expected results:

don't crash

Comment 1

[David Mandelin [:dmandelin]]

Luke, this is crashing on CrashIfInvalidSlot called from

  http://hg.mozilla.org/mozilla-central/annotate/5c13fce74f83/js/src/vm/Stack.cpp#l1159

any idea offhand what that means?

Comment 2

[Luke Wagner [:luke]]

Ooh yeah, this may be STR for bug 723445!  I'll investigate.

Comment 3

[Luke Wagner [:luke]]

Wow, this is a most excellent test case; thanks!  I can reproduce locally, I'll look into it hopefully tomorrow.

Comment 4

[Luke Wagner [:luke]]

Attachment: fix forced return

Ah, I see the bug.  The problem is that forced_return (jumped to by the debugger) is setting the stack depth to 0, but leaving pc pointing to the JSOP_CALL which the debugger interrupted.  Thus, when the ScriptDebugEpilogue runs, js_ReconstructStackDepth(pc) is not equal to the actual stack depth and we go touching invalid memory (the next frame).

Thank you again Attila for taking the time to create a reproducible test-case.  It was certainly invaluable!  We've been trying to track down reports of this crash for a while and between this and bug 723445, I bet we have it fixed.

Comment 5

[Luke Wagner [:luke]]

I forgot, I'll make a shell test-case tomorrow.

Comment 6

[Luke Wagner [:luke]]

Attachment: fix forced return

This patch adds a shell testcase.  In finding a testcase, I can see why this was relatively hard to hit: you have to trap on a 'call' instruction, force an early return, then, in the leave-frame hook for that function, you need to runs some code that inspects the stack via StackIter.  Phew.

Comment 7

[Luke Wagner [:luke]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/4e2d0a1a9edd

Comment 8

[(no longer active)]

https://hg.mozilla.org/mozilla-central/rev/4e2d0a1a9edd