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From 7dd9696a1b288746bac6fa0fe4f1d212be4f8f82 Mon Sep 17 00:00:00 2001
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From: jmaloy <jmaloy@redhat.com>
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Date: Wed, 29 Jan 2020 21:41:15 +0000
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Subject: [PATCH 2/6] iscsi: Cap block count from GET LBA STATUS
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(CVE-2020-1711)
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: jmaloy <jmaloy@redhat.com>
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Message-id: <20200129214115.19979-3-jmaloy@redhat.com>
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Patchwork-id: 93585
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O-Subject: [RHEL-8.2.0 qemu-kvm PATCH 2/2] iscsi: Cap block count from GET LBA STATUS (CVE-2020-1711)
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Bugzilla: 1794501
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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From: Felipe Franciosi <felipe@nutanix.com>
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When querying an iSCSI server for the provisioning status of blocks (via
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GET LBA STATUS), Qemu only validates that the response descriptor zero's
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LBA matches the one requested. Given the SCSI spec allows servers to
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respond with the status of blocks beyond the end of the LUN, Qemu may
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have its heap corrupted by clearing/setting too many bits at the end of
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its allocmap for the LUN.
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A malicious guest in control of the iSCSI server could carefully program
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Qemu's heap (by selectively setting the bitmap) and then smash it.
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This limits the number of bits that iscsi_co_block_status() will try to
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update in the allocmap so it can't overflow the bitmap.
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Fixes: CVE-2020-1711
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Cc: qemu-stable@nongnu.org
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Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
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Signed-off-by: Peter Turschmid <peter.turschm@nutanix.com>
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Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 693fd2acdf14dd86c0bf852610f1c2cca80a74dc)
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Signed-off-by: Jon Maloy <jmaloy@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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block/iscsi.c | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/block/iscsi.c b/block/iscsi.c
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index 336ce49..8ec97ab 100644
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--- a/block/iscsi.c
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+++ b/block/iscsi.c
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@@ -671,7 +671,7 @@ static int coroutine_fn iscsi_co_block_status(BlockDriverState *bs,
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struct scsi_get_lba_status *lbas = NULL;
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struct scsi_lba_status_descriptor *lbasd = NULL;
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struct IscsiTask iTask;
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- uint64_t lba;
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+ uint64_t lba, max_bytes;
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int ret;
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iscsi_co_init_iscsitask(iscsilun, &iTask);
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@@ -691,6 +691,7 @@ static int coroutine_fn iscsi_co_block_status(BlockDriverState *bs,
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}
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lba = offset / iscsilun->block_size;
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+ max_bytes = (iscsilun->num_blocks - lba) * iscsilun->block_size;
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qemu_mutex_lock(&iscsilun->mutex);
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retry:
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@@ -734,7 +735,7 @@ retry:
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goto out_unlock;
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}
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- *pnum = (int64_t) lbasd->num_blocks * iscsilun->block_size;
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+ *pnum = MIN((int64_t) lbasd->num_blocks * iscsilun->block_size, max_bytes);
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if (lbasd->provisioning == SCSI_PROVISIONING_TYPE_DEALLOCATED ||
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lbasd->provisioning == SCSI_PROVISIONING_TYPE_ANCHORED) {
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--
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1.8.3.1
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