linux-kernel - Bug: getcwd: cannot access parent directories

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAGQTitMPcrHRhFVLfApe21T7hYyeX05ffuSJj452+f+ZksmQqg@mail.gmail.com>
Date:   Fri, 21 Sep 2018 18:16:26 +1000
From:   Roel Van de Paar <roel.vandepaar@...cona.com>
To:     linux-kernel@...r.kernel.org
Subject: Bug: getcwd: cannot access parent directories

[1.] One line summary of the problem:

"cd: error retrieving current directory: getcwd: cannot access parent
directories: No such file or directory" on move of directories to
another volume

[2.] Full description of the problem/report:

Example output (testcase below):

/tmp/1/2$ cd ..
cd: error retrieving current directory: getcwd: cannot access parent
directories: No such file or directory
/tmp/1/2/..$ cd ..
cd: error retrieving current directory: getcwd: cannot access parent
directories: No such file or directory
/tmp/1/2/../..$ cd ..
cd: error retrieving current directory: getcwd: cannot access parent
directories: No such file or directory
/tmp/1/2/../../..$ cd ..
cd: error retrieving current directory: getcwd: cannot access parent
directories: No such file or directory
/tmp/1/2/../../../..$ cd ..
cd: error retrieving current directory: getcwd: cannot access parent
directories: No such file or directory
/tmp/1/2/../../../../..$ cd ..
cd: error retrieving current directory: getcwd: cannot access parent
directories: No such file or directory
/tmp/1/2/../../../../../..$ cd ..
/tmp$

- The number of ".." required is not correct
- The number of ".." matches the number of subdirs (see below)

[4.] Kernel information

Tested on latest updates of:
* Ubuntu Xenial
* Ubuntu Bionic
* Centos 7

[7.] A small shell script or example program which triggers the
problem (if possible)

In session 1
  cd /tmp
  mkdir -p 1/2
  cd 1/2

In session 2 (another terminal session)
  cd /tmp
  mkdir -p 3/4/5/6/7
  mv 1 3/4/5/6/7
  mv 3 /dev/shm   # where /dev/shm is some other disk. /dev/shm
reproduction works too. If the disk is the same, the issue will not
show.

Back to session 1
  cd ..   # fail
  cd ..   # fail
  cd ..   # fail
  cd ..   # fail
  cd ..   # fail
  cd ..   # fail
  cd ..   # works, but to completely incorrect directory given the
many 'cd ..'```

The problem is made more clear here by using 3/4/5/6/7 but you can
also just use a single subdir to see it