[tbb-bugs] #22788 [Applications/Tor Browser]: PDF.js overloads CPU when opening large PDFs on higher security slider levels

[Tor Bug Tracker & Wiki]

#22788: PDF.js overloads CPU when opening large PDFs on higher security slider
levels
--------------------------------------+--------------------------
 Reporter:  teor                      |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  tbb-security-slider       |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
--------------------------------------+--------------------------

Comment (by cypherpunks):

 This is not an issue with JIT simply being too slow, or at least that's
 not the only issue. Extremely javascript-heavy webpages that are nearly
 unusable without JIT still do not result in this behavior, and it only
 applies to some PDF files, even ones which do not seem particularly
 complicated. Likewise, for PDF files which do not trigger this hang, the
 lack of JIT simply makes them render more slowly. As gk mentioned, the PDF
 viewer is blocking the web content process. My guess is that some behavior
 changed which results in some element in the file taking up way more CPU
 than it needs to, resulting in even simple PDF files hanging the process.

 I would eat my hat if this were merely a case of "this is slow for big
 PDFs because no JIT".

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22788#comment:8>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online