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Groups > linux.debian.bugs.dist > #1049565

Bug#983405: adduser: race conditions in adduser

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Package: adduser
Version: 3.116ubuntu1
Severity: important

Dear Maintainer,

*** Reporter, please consider answering these questions, where appropriate ***

   * What led up to the situation?

A custom designed system service attempted to add several users near-
simultaneously.  I got two users created with the same GID.  One of them had no
home directory.

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

I deleted the users and manually re-added them.

Then I modified the custom service to protect the call to adduser with a POSIX
semaphore.

   * What was the outcome of this action?

I fixed the immediate problem by hand, and I expect that the semaphore will
prevent the same problem for this particular service.

   * What outcome did you expect instead?

adduser should protect itself against these kind of race conditions.

*** End of the template - remove these template lines ***



-- System Information:
Debian Release: buster/sid
  APT prefers bionic-updates
  APT policy: (500, 'bionic-updates'), (500, 'bionic-security'), (500, 'bionic'), (100, 'bionic-backports')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.15.0-135-generic (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages adduser depends on:
ii  debconf [debconf-2.0]  1.5.66ubuntu1
ii  passwd                 1:4.5-1ubuntu2

adduser recommends no packages.

Versions of packages adduser suggests:
ii  ecryptfs-utils          111-0ubuntu5
ii  liblocale-gettext-perl  1.07-3build2
ii  perl                    5.26.1-6ubuntu0.5

-- debconf information:
  adduser/homedir-permission: true
  adduser/title:

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Bug#983405: adduser: race conditions in adduser Brent Baccala <cosine@freesoft.org> - 2021-02-23 18:30 +0100

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