The current setup of the quarantine page tables assumes that the
quarantine domain (dom_io) has been initialized with an address width
of DEFAULT_DOMAIN_ADDRESS_WIDTH (48) and hence 4 page table levels.
However dom_io being a PV domain gets the AMD-Vi IOMMU page tables
levels based on the maximum (hot pluggable) RAM address, and hence on
systems with no RAM above the 512GB mark only 3 page-table levels are
configured in the IOMMU.
On systems without RAM above the 512GB boundary
amd_iommu_quarantine_init() will setup page tables for the scratch
page with 4 levels, while the IOMMU will be configured to use 3 levels
only, resulting in the last page table directory (PDE) effectively
becoming a page table entry (PTE), and hence a device in quarantine
mode gaining write access to the page destined to be a PDE.
Due to this page table level mismatch, the sink page the device gets
read/write access to is no longer cleared between device assignment,
possibly leading to data leaks.
CVSS Score
5.5
EPSS Score
0.001
Published
2024-01-05
The fixes for XSA-422 (Branch Type Confusion) and XSA-434 (Speculative
Return Stack Overflow) are not IRQ-safe. It was believed that the
mitigations always operated in contexts with IRQs disabled.
However, the original XSA-254 fix for Meltdown (XPTI) deliberately left
interrupts enabled on two entry paths; one unconditionally, and one
conditionally on whether XPTI was active.
As BTC/SRSO and Meltdown affect different CPU vendors, the mitigations
are not active together by default. Therefore, there is a race
condition whereby a malicious PV guest can bypass BTC/SRSO protections
and launch a BTC/SRSO attack against Xen.
CVSS Score
4.7
EPSS Score
0.0
Published
2024-01-05
Arm provides multiple helpers to clean & invalidate the cache
for a given region. This is, for instance, used when allocating
guest memory to ensure any writes (such as the ones during scrubbing)
have reached memory before handing over the page to a guest.
Unfortunately, the arithmetics in the helpers can overflow and would
then result to skip the cache cleaning/invalidation. Therefore there
is no guarantee when all the writes will reach the memory.
This undefined behavior was meant to be addressed by XSA-437, but the
approach was not sufficient.
CVSS Score
3.3
EPSS Score
0.0
Published
2024-01-05
Arm provides multiple helpers to clean & invalidate the cache
for a given region. This is, for instance, used when allocating
guest memory to ensure any writes (such as the ones during scrubbing)
have reached memory before handing over the page to a guest.
Unfortunately, the arithmetics in the helpers can overflow and would
then result to skip the cache cleaning/invalidation. Therefore there
is no guarantee when all the writes will reach the memory.
CVSS Score
3.3
EPSS Score
0.0
Published
2024-01-05
For migration as well as to work around kernels unaware of L1TF (see
XSA-273), PV guests may be run in shadow paging mode. Since Xen itself
needs to be mapped when PV guests run, Xen and shadowed PV guests run
directly the respective shadow page tables. For 64-bit PV guests this
means running on the shadow of the guest root page table.
In the course of dealing with shortage of memory in the shadow pool
associated with a domain, shadows of page tables may be torn down. This
tearing down may include the shadow root page table that the CPU in
question is presently running on. While a precaution exists to
supposedly prevent the tearing down of the underlying live page table,
the time window covered by that precaution isn't large enough.
CVSS Score
7.8
EPSS Score
0.001
Published
2024-01-05
When a transaction is committed, C Xenstored will first check
the quota is correct before attempting to commit any nodes. It would
be possible that accounting is temporarily negative if a node has
been removed outside of the transaction.
Unfortunately, some versions of C Xenstored are assuming that the
quota cannot be negative and are using assert() to confirm it. This
will lead to C Xenstored crash when tools are built without -DNDEBUG
(this is the default).
CVSS Score
5.5
EPSS Score
0.001
Published
2024-01-05
[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]
libfsimage contains parsing code for several filesystems, most of them based on
grub-legacy code. libfsimage is used by pygrub to inspect guest disks.
Pygrub runs as the same user as the toolstack (root in a priviledged domain).
At least one issue has been reported to the Xen Security Team that allows an
attacker to trigger a stack buffer overflow in libfsimage. After further
analisys the Xen Security Team is no longer confident in the suitability of
libfsimage when run against guest controlled input with super user priviledges.
In order to not affect current deployments that rely on pygrub patches are
provided in the resolution section of the advisory that allow running pygrub in
deprivileged mode.
CVE-2023-4949 refers to the original issue in the upstream grub
project ("An attacker with local access to a system (either through a
disk or external drive) can present a modified XFS partition to
grub-legacy in such a way to exploit a memory corruption in grub’s XFS
file system implementation.") CVE-2023-34325 refers specifically to
the vulnerabilities in Xen's copy of libfsimage, which is decended
from a very old version of grub.
CVSS Score
7.8
EPSS Score
0.001
Published
2024-01-05
The caching invalidation guidelines from the AMD-Vi specification (48882—Rev
3.07-PUB—Oct 2022) is incorrect on some hardware, as devices will malfunction
(see stale DMA mappings) if some fields of the DTE are updated but the IOMMU
TLB is not flushed.
Such stale DMA mappings can point to memory ranges not owned by the guest, thus
allowing access to unindented memory regions.
CVSS Score
7.8
EPSS Score
0.0
Published
2024-01-05
Cortex-A77 cores (r0p0 and r1p0) are affected by erratum 1508412
where software, under certain circumstances, could deadlock a core
due to the execution of either a load to device or non-cacheable memory,
and either a store exclusive or register read of the Physical
Address Register (PAR_EL1) in close proximity.
CVSS Score
5.5
EPSS Score
0.0
Published
2023-12-08
The fix for XSA-423 added logic to Linux'es netback driver to deal with
a frontend splitting a packet in a way such that not all of the headers
would come in one piece. Unfortunately the logic introduced there
didn't account for the extreme case of the entire packet being split
into as many pieces as permitted by the protocol, yet still being
smaller than the area that's specially dealt with to keep all (possible)
headers together. Such an unusual packet would therefore trigger a
buffer overrun in the driver.
CVSS Score
7.8
EPSS Score
0.0
Published
2023-09-22
Page 1