[PATCH 04/13] sg_io: resolve conflicts between commands assigned to multiple classes (CVE-2012-4542)

Paolo Bonzini
2013-01-24T15:08:31Z

Some SCSI commands can be sent to disks via SG_IO even by unprivileged
users. Unfortunately, some opcodes overlap across SCSI device classes
and have different meanings for different classes. Four of them can
be used for read-only file descriptors on MMC, but should be limited to
descriptors opened for read-write on SBC:

The current bitmap of allowed commands is designed for MMC devices
(roughly, "play/burn CDs without requiring root").

- READ SUBCHANNEL <-> UNMAP (destructive, but no control on written
data)

- GET PERFORMANCE <-> ERASE (not really a problem, no one supports
ERASE anyway)

- READ DISC INFORMATION <-> XPWRITE (not commonly implemented but
most dangerous)

- PLAY AUDIO TI <-> SANITIZE (a very new command)

To fix this, the series splits the bitmap entries for these four
commands into two entries, one read-only for MMC and one read-write
for the other device classes.

Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: linux-scsi@kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
block/scsi_ioctl.c | 12 ++++++++----
1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index e68add2..c266546 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -181,29 +181,33 @@ static void blk_set_cmd_filter_defaults(struct blk_cmd_filter *filter)
sgio_bitmap_set(0x2E, D| W|R|O| B|K , write); // WRITE AND VERIFY(10)
sgio_bitmap_set(0x35, D| W|R|O| B|K , write); // SYNCHRONIZE CACHE(10)
sgio_bitmap_set(0x3F, D| W| O , write); // WRITE LONG(10)
+ sgio_bitmap_set(0x42, D , write); // UNMAP
+ sgio_bitmap_set(0x48, D| B , write); // SANITIZE
+ sgio_bitmap_set(0x51, D , write); // XPWRITE(10)
sgio_bitmap_set(0x8A, D|T| W| O| B , write); // WRITE(16)
sgio_bitmap_set(0xAA, D| W|R|O| C , write); // WRITE(12)
+ sgio_bitmap_set(0xAC, O , write); // ERASE(12)
sgio_bitmap_set(0xAE, D| W| O , write); // WRITE AND VERIFY(12)
sgio_bitmap_set(0xEA, D| W| O , write); // WRITE_LONG_2 ??

/* (mostly) MMC */

sgio_bitmap_set(0x23, R , read); // READ FORMAT CAPACITIES
- sgio_bitmap_set(0x42, D| R , read); // READ SUB-CHANNEL / UNMAP !!
+ sgio_bitmap_set(0x42, R , read); // READ SUB-CHANNEL
sgio_bitmap_set(0x43, R , read); // READ TOC/PMA/ATIP
sgio_bitmap_set(0x44, T| R| V , read); // READ HEADER
sgio_bitmap_set(0x45, R , read); // PLAY AUDIO(10)
sgio_bitmap_set(0x46, R , read); // GET CONFIGURATION
sgio_bitmap_set(0x47, R , read); // PLAY AUDIO MSF
- sgio_bitmap_set(0x48, D| R| B , read); // PLAY AUDIO TI / SANITIZE !!
+ sgio_bitmap_set(0x48, R , read); // PLAY AUDIO TI
sgio_bitmap_set(0x4A, R , read); // GET EVENT STATUS NOTIFICATION
sgio_bitmap_set(0x4B, R , read); // PAUSE/RESUME
sgio_bitmap_set(0x4E, R , read); // STOP PLAY/SCAN
- sgio_bitmap_set(0x51, D| R , read); // READ DISC INFORMATION / XPWRITE(10) !!
+ sgio_bitmap_set(0x51, R , read); // READ DISC INFORMATION
sgio_bitmap_set(0x52, R , read); // READ TRACK INFORMATION
sgio_bitmap_set(0x5C, R , read); // READ BUFFER CAPACITY
sgio_bitmap_set(0xA4, R , read); // REPORT KEY
- sgio_bitmap_set(0xAC, R|O , read); // GET PERFORMANCE / ERASE !!
+ sgio_bitmap_set(0xAC, R , read); // GET PERFORMANCE
sgio_bitmap_set(0xAD, R , read); // READ DVD STRUCTURE
sgio_bitmap_set(0xB9, R , read); // READ CD MSF
sgio_bitmap_set(0xBA, R , read); // SCAN
--
1.7.1