[Bug 1605732] [NEW] Entering a long, invalid command to the terminal freezes the system

[Aku Viljanen]

Public bug reported:

If I enter an invalid command that is a few thousand characters long it
goes to the command-not-found program, and it starts to look for it in
the repositories. This takes up a lot of RAM, and the whole system
freezes.


By default, /usr/lib/command-not-found contains these lines:

    if len(args) == 1:
        cnf = CommandNotFound(options.data_dir)
        if not cnf.advise(args[0], options.ignore_installed) and not options.no_failure_msg:
            print(_("%s: command not found") % args[0], file=sys.stderr)


Adding a simple length check is enough to completely solve this problem.

    if len(args) == 1:
        # Fix crashing with long commands
        if len(args[0]) > 50:
            print(_("%s: command not found") % args[0], file=sys.stderr)
        else:
            cnf = CommandNotFound(options.data_dir)
            if not cnf.advise(args[0], options.ignore_installed) and not options.no_failure_msg:
                print(_("%s: command not found") % args[0], file=sys.stderr)


I'm having this issue in Ubuntu 14.04.04 with command-not-found 0.3ubuntu12, but the same code is in 16.10's packages.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: command-not-found 0.3ubuntu12 [modified: usr/lib/command-not-found]
ProcVersionSignature: Ubuntu 4.2.0-42.49~14.04.1-generic 4.2.8-ckt12
Uname: Linux 4.2.0-42-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
CurrentDesktop: MATE
Date: Fri Jul 22 19:12:59 2016
PackageArchitecture: all
SourcePackage: command-not-found
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: command-not-found (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug trusty

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to command-not-found in Ubuntu.
https://bugs.launchpad.net/bugs/1605732

Title:
  Entering a long, invalid command to the terminal freezes the system

Status in command-not-found package in Ubuntu:
  New

Bug description:
  If I enter an invalid command that is a few thousand characters long
  it goes to the command-not-found program, and it starts to look for it
  in the repositories. This takes up a lot of RAM, and the whole system
  freezes.

  
  By default, /usr/lib/command-not-found contains these lines:

      if len(args) == 1:
          cnf = CommandNotFound(options.data_dir)
          if not cnf.advise(args[0], options.ignore_installed) and not options.no_failure_msg:
              print(_("%s: command not found") % args[0], file=sys.stderr)

  
  Adding a simple length check is enough to completely solve this problem.

      if len(args) == 1:
          # Fix crashing with long commands
          if len(args[0]) > 50:
              print(_("%s: command not found") % args[0], file=sys.stderr)
          else:
              cnf = CommandNotFound(options.data_dir)
              if not cnf.advise(args[0], options.ignore_installed) and not options.no_failure_msg:
                  print(_("%s: command not found") % args[0], file=sys.stderr)

  
  I'm having this issue in Ubuntu 14.04.04 with command-not-found 0.3ubuntu12, but the same code is in 16.10's packages.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: command-not-found 0.3ubuntu12 [modified: usr/lib/command-not-found]
  ProcVersionSignature: Ubuntu 4.2.0-42.49~14.04.1-generic 4.2.8-ckt12
  Uname: Linux 4.2.0-42-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.21
  Architecture: amd64
  CurrentDesktop: MATE
  Date: Fri Jul 22 19:12:59 2016
  PackageArchitecture: all
  SourcePackage: command-not-found
  UpgradeStatus: No upgrade log present (probably fresh install)

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/command-not-found/+bug/1605732/+subscriptions