571289 - XPConnect uses nsScriptSecurityManager off the main thread [@ nsScriptSecurityManager::CheckPropertyAccessImpl(unsigned int, nsAXPCNativeCallContext*, JSContext*, JSObject*, nsISupports*, nsIURI*, nsIClassInfo*, char const*, int, void**) ]

Status: RESOLVED FIXED

(Core :: XPConnect, defect)

Description

[Blake Kaplan (:mrbkap) (inactive)]

We've seen a couple reports where extensions that run JS code that deals with XPConnect off the main thread end up calling into nsScriptSecurityManager and then crashing (http://crash-stats.mozilla.com/report/index/2dcc69c6-ff24-4d30-9594-ba34f2100517 is one example).

We need to figure out why XPConnect is getting a hold of the main thread's security manager on these other threads. Without this, any extension that runs JS off the main thread (even if it's careful about what objects it uses off the main thread) risks crashing.

Comment 1

[timeless]

http://mxr.mozilla.org/mozilla-central/ident?i=GetSecurityManager

All of the magic wrapper code uses this which accesses a global

1048 XPCConvert::NativeInterface2JSObject(XPCLazyCallContext& lccx,
1244         if(NS_SUCCEEDED(rv) && wrapper)
1255             if (allowNativeWrapper &&
1256                 !xpc_SameScope(wrapper->GetScope(), xpcscope, &sameOrigin))
1309                 if(!JS_IsSystemObject(ccx, flat))
1329                         nsIScriptSecurityManager *ssm =
1330                             XPCWrapper::GetSecurityManager();

Comment 2

[Blake Kaplan (:mrbkap) (inactive)]

Surprisingly, that's not actually the problem (I have no clue why, I suspect it might be because it's impossible for !xpc_SameScope to be true off the main thread). The problem shown in the crash report in comment 0 is that the "default" security manager for a not-main thread is not null, which is definitely a bug.

Comment 3

[Justin Lebar (not reading bugmail)]

For my reference, these are my notes from talking with mrbkap about how to reproduce this issue:

From chrome, using nsIThreadManager, dispatch a runnable to some other code I own.

Touch xpconnect. Create an object using Components.classes.(some threadsafe interface), then touch it in a way that isn't quickstubbed.

Maybe crashes in nsScriptSecurityManager (somewhere), due to bug in GetDefaultSecurityManager.
 * Could put NS_ABORT_IF_FALSE(IsMainThread) in nsScriptSecurityManager::CanAccess

Comment 4

[Justin Lebar (not reading bugmail)]

Attachment: Testcase

Testcase.  The new browser test triggers an assertion I added to GetDefaultSecurityManager and kills the browser.

Comment 5

[Justin Lebar (not reading bugmail)]

Attachment: Patch v1

Returns null when we're not the main thread.

Comment 6

[Josh Matthews [:jdm]]

qref, perhaps?

Comment 7

[Justin Lebar (not reading bugmail)]

Attachment: Patch v1.1

Ack, sorry.  qref'ed.

Comment 8

[Justin Lebar (not reading bugmail)]

Blake, since this is crashing plugins, should this block?

Comment 9

[Janek B.]

Yes please. Firefox crashes every few minutes and that really gets my goat.

Comment 10

[Blake Kaplan (:mrbkap) (inactive)]

Yeah, I think so.

Comment 11

[Janek B.]

Could you please manage fixing this already in the next release? Current Firefox is nearly unusable because of so many crashes (mainly invoked by Yoono which I don't want to miss) and I don't want to switch back to 3.6.4 (should be Xulrunner 1.9.2.4, right?) where the problem didn't exist.

Comment 14

[LegNeato]

We want this on the branch but wouldn't block a release on it, as it looks like there are only ~1000 crashes total per release. Please ask for approval on the patch when ready and we'll get it in the current in-flight update.

Comment 15

[LegNeato]

Is there a possibility of our own code calling nsScriptSecurityManager off the main thread and thus this fix would cause issues?

Comment 17

[Justin Lebar (not reading bugmail)]

http://hg.mozilla.org/mozilla-central/rev/46310d87f848

Comment 18

[Justin Lebar (not reading bugmail)]

Whoops; didn't mean to resolve this, since we still need to land on branches.

Comment 19

[LegNeato]

Does this same fix apply to 1.9.1? We have it marked needed there as well. Approving for 1.9.2.11. Please ask for approval for 1.9.1.14 if it is needed there as well.

Comment 20

[Daniel Veditz [:dveditz]]

We use the status1.9.x fields to track branch status

Comment 21

[Daniel Veditz [:dveditz]]

IOW change status1.9.2 from "wanted" to ".11-fixed" when you land, and similarly for the 1.9.1 branch

Comment 22

[Johnny Stenback (:jst)]

Fixed on branches.

http://hg.mozilla.org/releases/mozilla-1.9.2/rev/89508ed59ad9
http://hg.mozilla.org/releases/mozilla-1.9.1/rev/3affdd6e23e8

Comment 23

[Al Billings [:abillings - ex-MoCo]]

Verified for 1.9.1 and 1.9.2 based on passing unit test.