[Bug 1587101] Re: Grep silently discards tails of long text streams

[Seth Arnold]

** Information type changed from Private Security to Public Security

** Changed in: grep (Ubuntu)
       Status: New => Invalid

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Title:
  Grep silently discards tails of long text streams

Status in grep package in Ubuntu:
  Invalid

Bug description:
  Grep silently discards tails of long streams on my machine:

  grep -n discharge_calculate_.m 0.txt 
  64264:/home/pia/phd/src/discharge/discharge_calculate_.m

  So far, so good, "discharge_calculate_.m" is grepped on line 64264.

  grep -n discharge 0.txt | grep calculate

  Apparently, grep gobbled, and fails to grep the line.

  Some tests:

  tail -n +64264 0.txt | grep discharge | grep calculate_
  /home/pia/phd/src/discharge/discharge_calculate_.m

  grep -a -n discharge 0.txt | grep calculate_
  64264:/home/pia/phd/src/discharge/discharge_calculate_.m

  file 0.txt 
  0.txt: ISO-8859 text

  I noticed this when not finding files that I knew to exist in the directory tree and
  thought at first it were a bug in locate or find. I could not reproduce this on the fly when the lines leading to the grep line were filled with arbitrary characters, so the behaviour depends also on the content of the stream, not only on its length. Grep seems to interpret the text stream as binary. Looks very much like a buffer overflow, that's why I mark this as a security vulnerability. In case this is intended behaviour, grep should not silently discard the tail but output a warning to stderr. A less than 60k line limit seems also a bit too low in the 64bit era.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: grep 2.25-1~16.04.1
  ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
  Uname: Linux 4.4.0-22-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  CurrentDesktop: GNOME
  Date: Mon May 30 15:41:35 2016
  InstallationDate: Installed on 2015-11-05 (207 days ago)
  InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
  SourcePackage: grep
  UpgradeStatus: No upgrade log present (probably fresh install)

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