[Bug 2055402] Re: Though lintian call: error: troff: Segmentation fault

[Colin Watson]

I would like to add a small correction here regarding the intent of man-
db's AppArmor policy.  The intent is _not_ to confine where the man
program itself can write, as is noted in the policy itself:

  # Allow basically anything in terms of file system access, subject to DAC.
  # The purpose of this profile isn't to confine man itself (that might be
  # nice in the future, but is tricky since it's quite configurable), but to
  # confine the processes it calls that parse untrusted data.
  /** mrixwlk,

However, the man_groff sub-profile is more constrained, and that's used
for the groff-related subprocesses that man forks.  That's what's
triggering denials here.

In some ways I wonder if that means that the problem is a leaky
abstraction of sorts.  We're trying to confine man's groff-related
subprocesses, but we pass through FDs to them.  One possibility might be
to have groff write to a pipe instead in this situation and stream it
through man to the output file.  Slightly less efficient, but it might
not be too unreasonable.

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Title:
  Though lintian call: error: troff: Segmentation fault

Status in lintian package in Ubuntu:
  Confirmed

Bug description:
  groff crash when redirecting output to a file

  % man --warnings -E UTF-8 -l -Tutf8 -Z /usr/share/man/man1/cat.1.gz >output
  troff:<standard input>:3: fatal error: unable to flush output file: Permission denied
  groff: error: troff: Segmentation fault (core dumped)
  man: command exited with status 2: /usr/libexec/man-db/zsoelim | /usr/libexec/man-db/manconv -f UTF-8:ISO-8859-1 -t UTF-8//IGNORE | preconv -e UTF-8 | tbl | groff -mandoc -Z -rLL=78n -rLT=78n -wmac -Tutf8

  This is typically triggered by lintian when scanning man pages

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