1297054 - [Static Analysis][Dereference before null check] in function CanvasRenderingContext2D::InitializeWithDrawTarget

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Andi [:andi]]

The Static Analysis tool Coverity detected that |aTarget| is dereferenced before begin null checked:

>>  IntSize size = aTarget->GetSize();
>>  SetDimensions(size.width, size.height);
>>
>>  if (aTarget) {
>>    mTarget = aTarget;
>>    mBufferProvider = new PersistentBufferProviderBasic(aTarget);
>>  } else {
>>    EnsureErrorTarget();
>>    mTarget = sErrorTarget;
>>  }

There is no posibility that in this context a null pointer dereference can occur since the context where InitializeWithDrawTarget gets called null check aTarget:

>>        RefPtr<DrawTarget> canvasTarget =
>>          drawTarget->CreateSimilarDrawTarget(size, drawTarget->GetFormat());
>>        if (!canvasTarget) {
>>          continue;
>>        }
>>
>>        nsICanvasRenderingContextInternal* ctx = canvas->GetContextAtIndex(0);
>>        if (!ctx) {
>>          continue;
>>        }
>>
>>        // Initialize the context with the new DrawTarget.
>>        ctx->InitializeWithDrawTarget(nullptr, canvasTarget);

Comment 1

[Andi [:andi]]

Attachment: Bug 1297054 - remove null check in CanvasRenderingContext2D::InitializeWithDrawTarget.

Review commit: https://reviewboard.mozilla.org/r/73304/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/73304/

Comment 2

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 8783511 [details]
Bug 1297054 - remove null check in CanvasRenderingContext2D::InitializeWithDrawTarget.

https://reviewboard.mozilla.org/r/73304/#review71192

Can you change the signature of IntializeWithDrawTarget to use NotNull<gfx::DrawTarget*> aTarget?

Comment 3

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 8783511 [details]
Bug 1297054 - remove null check in CanvasRenderingContext2D::InitializeWithDrawTarget.

https://reviewboard.mozilla.org/r/73304/#review71194

Comment 4

[Andi [:andi]]

Comment on attachment 8783511 [details]
Bug 1297054 - remove null check in CanvasRenderingContext2D::InitializeWithDrawTarget.

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/73304/diff/1-2/

Comment 5

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 8783511 [details]
Bug 1297054 - remove null check in CanvasRenderingContext2D::InitializeWithDrawTarget.

https://reviewboard.mozilla.org/r/73304/#review71696

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/97158ba1395d
remove null check in CanvasRenderingContext2D::InitializeWithDrawTarget. r=jrmuizel

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/97158ba1395d