[Bug 1026478] Re: CIFS: Files not shown in mount.smbfs directory listings

[Roman Fiedler]

I tried the "noserverino" workaround now and it worked.

Since without knowing that workaround, severe dataloss or more unlikely
malicious data hiding could occur on those machines, I would mandate to
make that option more prominent, e.g. to force mounts to have one of
"noserverino" or "serverino", but users not knowing about this option
will fail to mount and hence fail to suffer from data loss. Other option
would be, that if "noserverino" is always safe, that this should be the
default for mount.smbfs

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Title:
  CIFS: Files not shown in mount.smbfs directory listings

Status in “samba” package in Ubuntu:
  New

Bug description:
  The listing (dirread) of a CIFS-mounted share does not contain one file, but which is really available on the share. When accessing the file directly (stat or open call), the file can be accessed. The consequence of this issue is:
  * file is not included in copy/backup, since the directory listing fails to show it
  * attacker could hide arbitrary data from linux system.

  To reproduce:

  * Create files in a way, that you know, which files should be on the
  share. It is not clear, if this has to be done in a special way to
  trigger the problem (e.g. name length fill up buffers in a way to
  trigger +-1). On our system, pairs of files were created, so that it
  was obvious, that one of the pair was missing.

  * Run some ls tests:

   ** List all files in directory starting with one name
  (diropen/dirread):

  # ls -al log | grep '2007-08-23-syslog.1.'
  -rwxr-xr-x 1 root root 36 Oct 30 2009 2007-08-23-syslog.1.gz-lta.gpg.checksum

  ** List two named files (stat):

  # ls -al log/2007-08-23-syslog.1.gz-lta.gpg log/2007-08-23-syslog.1.gz-lta.gpg.checksum | grep '2007-08-23-syslog.1.'
  -rwxr-xr-x 1 root root 2148 Oct 30 2009 log/2007-08-23-syslog.1.gz-lta.gpg
  -rwxr-xr-x 1 root root 36 Oct 30 2009 og/2007-08-23-syslog.1.gz-lta.gpg.checksum

  * With additional echo 1 > /proc/fs/cifs/cifsFYI

  Both files show up in dmsg log:

  Jul 19 07:15:23 v3ls1203 kernel: [161751.469012] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: new entry cabaa1f0 old entry cabaa160
  Jul 19 07:15:23 v3ls1203 kernel: [161751.469017] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: For 2007-08-22-syslog.2.gz-lta.gpg.checksum
  Jul 19 07:15:23 v3ls1203 kernel: [161751.469023] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: new entry cabaa290 old entry cabaa1f0
  Jul 19 07:15:23 v3ls1203 kernel: [161751.469028] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: For 2007-08-23-syslog.1.gz-lta.gpg
  Jul 19 07:15:23 v3ls1203 kernel: [161751.469035] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: new entry cabaa320 old entry cabaa290
  Jul 19 07:15:23 v3ls1203 kernel: [161751.469041] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: For 2007-08-23-syslog.1.gz-lta.gpg.checksum
  Jul 19 07:15:23 v3ls1203 kernel: [161751.469047] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: new entry cabaa3c0 old entry cabaa320
  Jul 19 07:15:23 v3ls1203 kernel: [161751.469052] /build/buildd/linux-3.2.0/fs/cifs/readdir.c: For 2007-08-24-daemon.log-lta.gpg

  But 2007-08-23-syslog.1.gz-lta.gp  does not show up in the strace dump
  "strace -s256 -f ls log"

  
  Affects:
  =======

  * Ubuntu precise 32bit, fully updated

  # cat /proc/version
  Linux version 3.2.0-26-generic (buildd at lamiak) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) 0000041-Ubuntu SMP Thu Jun 14 16:26:01 UTC 2012

  # lsb_release -rd
  Description: Ubuntu 12.04 LTS
  Release: 12.04

  
  References:
  ==========

  * Might be similar bug from karmic: https://bugs.launchpad.net/ubuntu/+source/samba/+bug/406466
  * Possible other encounter: http://unix.stackexchange.com/questions/42140/weird-samba-and-gvfs-behavior-half-of-directories-files-randomly-appears-to-b/43454#43454

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