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authorPaolo Bonzini <pbonzini@redhat.com>2012-01-12 16:01:28 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-14 15:07:24 -0800
commit0bfc96cb77224736dfa35c3c555d37b3646ef35e (patch)
treeaf5135c929ee8e1bdb38c306b2634dbc547d5189 /block/scsi_ioctl.c
parent577ebb374c78314ac4617242f509e2f5e7156649 (diff)
downloadlinux-0bfc96cb77224736dfa35c3c555d37b3646ef35e.tar.gz
block: fail SCSI passthrough ioctls on partition devices
Linux allows executing the SG_IO ioctl on a partition or LVM volume, and will pass the command to the underlying block device. This is well-known, but it is also a large security problem when (via Unix permissions, ACLs, SELinux or a combination thereof) a program or user needs to be granted access only to part of the disk. This patch lets partitions forward a small set of harmless ioctls; others are logged with printk so that we can see which ioctls are actually sent. In my tests only CDROM_GET_CAPABILITY actually occurred. Of course it was being sent to a (partition on a) hard disk, so it would have failed with ENOTTY and the patch isn't changing anything in practice. Still, I'm treating it specially to avoid spamming the logs. In principle, this restriction should include programs running with CAP_SYS_RAWIO. If for example I let a program access /dev/sda2 and /dev/sdb, it still should not be able to read/write outside the boundaries of /dev/sda2 independent of the capabilities. However, for now programs with CAP_SYS_RAWIO will still be allowed to send the ioctls. Their actions will still be logged. This patch does not affect the non-libata IDE driver. That driver however already tests for bd != bd->bd_contains before issuing some ioctl; it could be restricted further to forbid these ioctls even for programs running with CAP_SYS_ADMIN/CAP_SYS_RAWIO. Cc: linux-scsi@vger.kernel.org Cc: Jens Axboe <axboe@kernel.dk> Cc: James Bottomley <JBottomley@parallels.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> [ Make it also print the command name when warning - Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'block/scsi_ioctl.c')
-rw-r--r--block/scsi_ioctl.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index a2c11f33087..260fa80ef57 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -24,6 +24,7 @@
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/cdrom.h>
+#include <linux/ratelimit.h>
#include <linux/slab.h>
#include <linux/times.h>
#include <asm/uaccess.h>
@@ -690,9 +691,53 @@ int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mod
}
EXPORT_SYMBOL(scsi_cmd_ioctl);
+int scsi_verify_blk_ioctl(struct block_device *bd, unsigned int cmd)
+{
+ if (bd && bd == bd->bd_contains)
+ return 0;
+
+ /* Actually none of these is particularly useful on a partition,
+ * but they are safe.
+ */
+ switch (cmd) {
+ case SCSI_IOCTL_GET_IDLUN:
+ case SCSI_IOCTL_GET_BUS_NUMBER:
+ case SCSI_IOCTL_GET_PCI:
+ case SCSI_IOCTL_PROBE_HOST:
+ case SG_GET_VERSION_NUM:
+ case SG_SET_TIMEOUT:
+ case SG_GET_TIMEOUT:
+ case SG_GET_RESERVED_SIZE:
+ case SG_SET_RESERVED_SIZE:
+ case SG_EMULATED_HOST:
+ return 0;
+ case CDROM_GET_CAPABILITY:
+ /* Keep this until we remove the printk below. udev sends it
+ * and we do not want to spam dmesg about it. CD-ROMs do
+ * not have partitions, so we get here only for disks.
+ */
+ return -ENOIOCTLCMD;
+ default:
+ break;
+ }
+
+ /* In particular, rule out all resets and host-specific ioctls. */
+ printk_ratelimited(KERN_WARNING
+ "%s: sending ioctl %x to a partition!\n", current->comm, cmd);
+
+ return capable(CAP_SYS_RAWIO) ? 0 : -ENOIOCTLCMD;
+}
+EXPORT_SYMBOL(scsi_verify_blk_ioctl);
+
int scsi_cmd_blk_ioctl(struct block_device *bd, fmode_t mode,
unsigned int cmd, void __user *arg)
{
+ int ret;
+
+ ret = scsi_verify_blk_ioctl(bd, cmd);
+ if (ret < 0)
+ return ret;
+
return scsi_cmd_ioctl(bd->bd_disk->queue, bd->bd_disk, mode, cmd, arg);
}
EXPORT_SYMBOL(scsi_cmd_blk_ioctl);