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iscsi: Cap block count from GET LBA STATUS (CVE-2020-1711) 

When querying an iSCSI server for the provisioning status of blocks (via
GET LBA STATUS), Qemu only validates that the response descriptor zero's
LBA matches the one requested. Given the SCSI spec allows servers to
respond with the status of blocks beyond the end of the LUN, Qemu may
have its heap corrupted by clearing/setting too many bits at the end of
its allocmap for the LUN.

A malicious guest in control of the iSCSI server could carefully program
Qemu's heap (by selectively setting the bitmap) and then smash it.

This limits the number of bits that iscsi_co_block_status() will try to
update in the allocmap so it can't overflow the bitmap.

Fixes: CVE-2020-1711
Cc: qemu-stable@nongnu.org
Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
Signed-off-by: Peter Turschmid <peter.turschm@nutanix.com>
Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 693fd2acdf)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
stable-4.2
Felipe Franciosi 2020-01-23 12:44:59 +00:00 committed by Michael Roth
parent 54bcaf08d6
commit 4e98c388d6
1 changed files with 3 additions and 2 deletions
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5
block/iscsi.c
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@ -701,7 +701,7 @@ static int coroutine_fn iscsi_co_block_status(BlockDriverState *bs,
struct scsi_get_lba_status *lbas = NULL;
struct scsi_lba_status_descriptor *lbasd = NULL;
struct IscsiTask iTask;
uint64_t lba;
uint64_t lba, max_bytes;
int ret;
iscsi_co_init_iscsitask(iscsilun, &iTask);
@ -721,6 +721,7 @@ static int coroutine_fn iscsi_co_block_status(BlockDriverState *bs,
}
lba = offset / iscsilun->block_size;
max_bytes = (iscsilun->num_blocks - lba) * iscsilun->block_size;
qemu_mutex_lock(&iscsilun->mutex);
retry:
@ -764,7 +765,7 @@ retry:
goto out_unlock;
}
*pnum = (int64_t) lbasd->num_blocks * iscsilun->block_size;
*pnum = MIN((int64_t) lbasd->num_blocks * iscsilun->block_size, max_bytes);
if (lbasd->provisioning == SCSI_PROVISIONING_TYPE_DEALLOCATED ||
lbasd->provisioning == SCSI_PROVISIONING_TYPE_ANCHORED) {