Re: [PATCH v2 00/14] Corrections and customization of the SG_IO commandwhitelist (CVE-2012-4542)
From: Paolo Bonzini
Date: Wed Feb 20 2013 - 11:13:12 EST
Il 06/02/2013 16:15, Paolo Bonzini ha scritto:
> 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 SCSI
> 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 this,
> 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.
Jens/James, is anyone going to pick this up for 3.9?
> 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(-)
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