1739366 - Assertion failure: tokenOffsetArg <= linebufLengthArg, at js/src/jsapi.cpp:3742 through StructuredClone

Status: RESOLVED FIXED

(Core :: IPC, defect, P1)

Description

[Christian Holler (:decoder)]

Using the fuzzing target in bug 1590068 (a target that uses dom::ipc::StructuredCloneData as its entry point to cover the StructuredCloneReader code that is browser-only), I was able to find the following crash on mozilla-central revision 9b9f8bfe2625+.

I also applied the patch in bug 1736046 to unblock the fuzzing.

Backtrace:

==16686==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f0987d2f179 bp 0x7fff8f149ed0 sp 0x7fff8f149ed0 T16686)
==16686==The signal is caused by a WRITE memory access.
==16686==Hint: address points to the zero page.
    #0 0x7f0987d2f179 in JSErrorReport::initBorrowedLinebuf(char16_t const*, unsigned long, unsigned long) js/src/jsapi.cpp:3742:3
    #1 0x7f09856e7bae in initOwnedLinebuf dist/include/js/ErrorReport.h:266:5
    #2 0x7f09856e7bae in mozilla::dom::ClonedErrorHolder::ToErrorValue(JSContext*, JS::MutableHandle<JS::Value>) dom/ipc/ClonedErrorHolder.cpp:312:16
    #3 0x7f09856e7314 in mozilla::dom::ClonedErrorHolder::ReadStructuredClone(JSContext*, JSStructuredCloneReader*, mozilla::dom::StructuredCloneHolder*) dom/ipc/ClonedErrorHolder.cpp:225:43
    #4 0x7f0982f0d676 in mozilla::dom::StructuredCloneHolder::CustomReadHandler(JSContext*, JSStructuredCloneReader*, JS::CloneDataPolicy const&, unsigned int, unsigned int) dom/base/StructuredCloneHolder.cpp:1005:12
    #5 0x7f0987c44805 in JSStructuredCloneReader::startRead(JS::MutableHandle<JS::Value>, js::gc::InitialHeap) js/src/vm/StructuredClone.cpp:2814:11
    #6 0x7f0987c348b2 in JSStructuredCloneReader::read(JS::MutableHandle<JS::Value>, unsigned long) js/src/vm/StructuredClone.cpp:3226:8
    #7 0x7f0987c34671 in ReadStructuredClone(JSContext*, JSStructuredCloneData const&, JS::StructuredCloneScope, JS::MutableHandle<JS::Value>, JS::CloneDataPolicy const&, JSStructuredCloneCallbacks const*, void*) js/src/vm/StructuredClone.cpp:705:12
    #8 0x7f0987c497c0 in JS_ReadStructuredClone(JSContext*, JSStructuredCloneData const&, unsigned int, JS::StructuredCloneScope, JS::MutableHandle<JS::Value>, JS::CloneDataPolicy const&, JSStructuredCloneCallbacks const*, void*) js/src/vm/StructuredClone.cpp:3382:10
    #9 0x7f0982f0b8bd in mozilla::dom::StructuredCloneHolder::ReadFromBuffer(nsIGlobalObject*, JSContext*, JSStructuredCloneData&, unsigned int, JS::MutableHandle<JS::Value>, JS::CloneDataPolicy const&, mozilla::ErrorResult&) dom/base/StructuredCloneHolder.cpp:409:8
    #10 0x7f0982f0b814 in mozilla::dom::StructuredCloneHolder::ReadFromBuffer(nsIGlobalObject*, JSContext*, JSStructuredCloneData&, JS::MutableHandle<JS::Value>, JS::CloneDataPolicy const&, mozilla::ErrorResult&) dom/base/StructuredCloneHolder.cpp:395:3
    #11 0x7f098575b271 in mozilla::dom::ipc::StructuredCloneData::Read(JSContext*, JS::MutableHandle<JS::Value>, JS::CloneDataPolicy const&, mozilla::ErrorResult&) dom/ipc/StructuredCloneData.cpp:116:3
    #12 0x7f09857559ae in mozilla::dom::ipc::StructuredCloneData::Read(JSContext*, JS::MutableHandle<JS::Value>, mozilla::ErrorResult&) dom/ipc/StructuredCloneData.cpp:104:3
    #13 0x7f098087c6f5 in FuzzingRunDomSC(unsigned char const*, unsigned long) dom/base/fuzztest/FuzzStructuredClone.cpp:59:10
    [...]

Marking s-s because of range assert. If this is not s-s, please keep it hidden anyway until we have completed landing of the parent target in bug 1590068.

Comment 1

[Christian Holler (:decoder)]

Attachment: Detailed Crash Information

Comment 2

[Christian Holler (:decoder)]

Attachment: Testcase

Comment 3

[Steve Fink [:sfink] [:s:]]

Attachment: Bug 1739366 - Ignore malformed cloned error

Comment 4

[Andrew McCreight [:mccr8]]

[Tracking Requested - why for this release]: The fuzzer that found this has been landed publicly, so we should be sure to uplift this fix.

Comment 5

[Andrew McCreight [:mccr8]]

I didn't check the code in branches, but I just assumed that this code is ancient.

Comment 6

[Steve Fink [:sfink] [:s:]]

Comment on attachment 9249314 [details]
Bug 1739366 - Ignore malformed cloned error

Security Approval Request

• How easily could an exploit be constructed based on the patch?: This allows arbitrary-sized out of bounds reads (and requires exploiting a content process first). I don't believe it can be used for writing.
• Do comments in the patch, the check-in comment, or tests included in the patch paint a bulls-eye on the security problem?: No
• Which older supported branches are affected by this flaw?: all
• If not all supported branches, which bug introduced the flaw?: None
• Do you have backports for the affected branches?: No
• If not, how different, hard to create, and risky will they be?: I expect it'll graft cleanly.
• How likely is this patch to cause regressions; how much testing does it need?: low risk, won't be hit unless someone manages to corrupt a structured clone, and when it is hit it leaves the affected value unset, which is already a common code path.

Comment 7

[Tom Ritter [:tjr] (OOTO until 4/30 at least)]

Comment on attachment 9249314 [details]
Bug 1739366 - Ignore malformed cloned error

Approved to land and request uplift

Comment 8

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/40592443e01f

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

As part of a security bug pattern analysis, we are requesting your help with a high level analysis of this bug. It is our hope to develop static analysis (or potentially runtime/dynamic analysis) in the future to identify classes of bugs.

Please visit this google form to reply.

Comment 10

[Dianna Smith [:diannaS]]

Steve, do you want to uplift this to beta?

Comment 11

[Andrew McCreight [:mccr8]]

Comment on attachment 9249314 [details]
Bug 1739366 - Ignore malformed cloned error

Beta/Release Uplift Approval Request

• User impact if declined: possible security issue
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): see the answer to the last question in comment 6
• String changes made/needed: none

Comment 12

[Dianna Smith [:diannaS]]

Comment on attachment 9249314 [details]
Bug 1739366 - Ignore malformed cloned error

Approved for 96.0b9

Comment 13

[Dianna Smith [:diannaS]]

https://hg.mozilla.org/releases/mozilla-beta/rev/71184b9b6cb5

Comment 14

[Ryan VanderMeulen [:RyanVM]]

Comment on attachment 9249314 [details]
Bug 1739366 - Ignore malformed cloned error

Approved for 91.5esr also.

Comment 15

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-esr91/rev/f003e26f65a5