[tbb-bugs] #23393 [Applications/Tor Browser]: All tabs often crash when closing one tab

Tor Bug Tracker & Wiki blackhole at torproject.org
Fri Sep 15 19:25:44 UTC 2017

#23393: All tabs often crash when closing one tab
 Reporter:  SaturnusDJ                           |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-e10s, tbb-crash,                 |  Actual Points:
  TorBrowserTeam201709R, GeorgKoppen201709       |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
Changes (by mcs):

 * cc: brade, mcs (added)
 * status:  assigned => needs_review
 * keywords:  tbb-e10s, tbb-crash, TorBrowserTeam201709, GeorgKoppen201709
     => tbb-e10s, tbb-crash, TorBrowserTeam201709R, GeorgKoppen201709


 I am not sure if there is just one underlying cause for this bug, but here
 is a fix for one scenario:

 The steps to reproduce are:
 1. Open https://www.google.com/ in a tab.
 2. Open https://developer.mozilla.org/samples/video/chroma-key/index.xhtml
 in a second tab.
 3. Click to play the video.
 4. After the canvas prompt is showing and while the video is still
 playing, close the tab.

 The developer.mozilla.org page tries repeatedly to extract canvas data,
 which means the canvas prompt codepath is being exercised over and over
 again, even while the tab is closing. This leads to an error in the
 main/parent process, after which it kills the content (child) process. I
 don't think this is exploitable from a security perspective, but it is
 disruptive if you have a few tabs open.

Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23393#comment:14>
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