[tor-bugs] #20283 [Applications/Tor Browser]: Tor Browser should run without a `/proc` filesystem.

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#20283: Tor Browser should run without a `/proc` filesystem.
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 Reporter:  yawning                   |          Owner:  pospeselr
     Type:  defect                    |         Status:  assigned
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  tbb-sandboxing            |  Actual Points:
Parent ID:  #20773                    |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by jld):

 If `SECCOMP_FILTER_FLAG_TSYNC` isn't available and `/proc/self/task` can't
 be listed, the sandbox can't start.  The process is already multithreaded,
 so we have to signal all the threads to tell them to apply seccomp, and we
 don't have access to the libc's internal list of threads (or the lock
 protecting it) so we have to ask the kernel via procfs.

 The single-threadedness check, however, has been removed in Firefox 60, as
 part of https://bugzilla.mozilla.org/show_bug.cgi?id=1401062.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20283#comment:10>
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