1651419 - nsDOMWindowUtils::CompareCanvases() checks img1, img2 for NULL after dereferencing them

Status: RESOLVED FIXED

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

Description

[Alexey Izbyshev]

img1 and img2 are dereferenced at https://searchfox.org/mozilla-central/rev/85ae3b91/dom/base/nsDOMWindowUtils.cpp#1301, but are checked for NULL only after that. Shouldn't the checks be moved up?

Comment 1

[Alphan Chen [:alchen]]

This line is added in bug 1428946.
Add author and reviewer to comment this.

Comment 2

[Alexey Izbyshev]

Even before that line was added, img1/img2 were dereferenced on creation of map1/map2 (https://searchfox.org/mozilla-central/rev/85ae3b91/dom/base/nsDOMWindowUtils.cpp#1306 via https://searchfox.org/mozilla-central/rev/85ae3b91/gfx/2d/2D.h#522).

Comment 3

[Bas Schouten (:bas.schouten)]

Correct :)

Comment 4

[Alphan Chen [:alchen]]

(In reply to Bas Schouten (:bas.schouten) from comment #3)

Correct :)

It looks like a good first bug for volunteer.

Hi Alexey,
it will be nice if you can contribute this fix. :)

https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/How_to_Submit_a_Patch

Comment 5

[Alexey Izbyshev]

The dereference before the NULL check was introduced in bug 1162357. I've added the author to CC (though he is on leave now) and submitted a patch.

Comment 6

[Alexey Izbyshev]

Attachment: Bug 1651419 - Check `img1/img2` for NULL before dereferencing them in nsDOMWindowUtils::CompareCanvases(). r?bas,alchen

Comment 7

[BugBot [:suhaib / :marco]]

This good-first-bug hasn't had any activity for 2 months, it is automatically unassigned.
For more information, please visit auto_nag documentation.

Comment 8

[Tim Nguyen :ntim]

Bas, is this ready to land?

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/52e0bdf9460f
Check `img1/img2` for NULL before dereferencing them in nsDOMWindowUtils::CompareCanvases(). r=bas,alchen

Comment 10

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/52e0bdf9460f