Features Download
From: Paolo Bonzini <pbonzini <at> redhat.com>
Subject: [PATCH v2 00/14] Corrections and customization of the SG_IO command whitelist (CVE-2012-4542)
Newsgroups: gmane.linux.kernel
Date: Wednesday 6th February 2013 15:15:47 UTC (over 3 years ago)
This series regards the whitelist that is used for the SG_IO ioctl.  This
whitelist has three problems:

* the bitmap of allowed commands is designed for MMC devices (roughly,
  "play/burn CDs without requiring root") but some opcodes overlap across
  device classes and have different meanings for different classes.

* also because the bitmap of allowed commands is designed for MMC devices
  only, some commands are missing even though they are generally useful and
  not insecure.  At least not more insecure than anything else you can
  do if you have access to /dev/sdX or /dev/stX nodes.

* the whitelist can be disabled per-process but not per-disk.  In addition,
  the required capability (CAP_SYS_RAWIO) gives access to a range of other 
  resources, enough to make it insecure.

The series corrects these problems.  Patches 1-4 solve the first problem,
which also has an assigned CVE, by using different bitmaps for the various
device classes.  Patches 5-11 solve the second by adding more commands
to the bitmaps.  Patches 12 and 13 solve the third, and were already
posted but ignored by the maintainers despite multiple pings.

Note: checkpatch hates the formatting of the command table.  I know about
and ensured that there are no errors in the rest of the code.  The current
formatting is IMHO quite handy, and roughly based on the files available
from the SCSI standard body.

Ok for the next merge window?


v1->v2: remove 2 MMC commands and 6 SBC commands (see patches 6 and 9
        for details).  Added patch 14 and added a few more scanner
        commands based on SANE (scanners are not whitelisted by default,
        also were not in v1, but this makes it possible to opt into the
        whitelist out of paranoia).  Removed C++ comments.  Removed the
        large #if 0'd list of commands that the kernel does not pass
        though.  Marked blk_set_cmd_filter_defaults as __init.

Paolo Bonzini (14):
  sg_io: pass request_queue to blk_verify_command
  sg_io: reorganize list of allowed commands
  sg_io: use different default filters for each device class
  sg_io: resolve conflicts between commands assigned to multiple
    classes (CVE-2012-4542)
  sg_io: whitelist a few more commands for rare & obsolete device types
  sg_io: whitelist another command for multimedia devices
  sg_io: whitelist a few more commands for media changers
  sg_io: whitelist a few more commands for tapes
  sg_io: whitelist a few more commands for disks
  sg_io: whitelist a few obsolete commands
  sg_io: mark blk_set_cmd_filter_defaults as __init
  sg_io: remove remnants of sysfs SG_IO filters
  sg_io: introduce unpriv_sgio queue flag
  sg_io: use unpriv_sgio to disable whitelisting for scanners

 Documentation/block/queue-sysfs.txt |    8 +
 block/blk-sysfs.c                   |   33 +++
 block/bsg.c                         |    2 +-
 block/scsi_ioctl.c                  |  369
 drivers/scsi/scsi_scan.c            |   14 ++-
 drivers/scsi/sg.c                   |    6 +-
 include/linux/blkdev.h              |    8 +-
 include/linux/genhd.h               |    9 -
 include/scsi/scsi.h                 |    3 +
 9 files changed, 344 insertions(+), 108 deletions(-)
CD: 30ms