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
[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
[This CNA information record relates to multiple CVEs; the
text explains which aspects/vulnerabilities correspond to which CVE.]
AMD CPUs since ~2014 have extensions to normal x86 debugging functionality.
Xen supports guests using these extensions.
Unfortunately there are errors in Xen's handling of the guest state, leading
to denials of service.
1) CVE-2023-34327 - An HVM vCPU can end up operating in the context of
a previous vCPUs debug mask state.
2) CVE-2023-34328 - A PV vCPU can place a breakpoint over the live GDT.
This allows the PV vCPU to exploit XSA-156 / CVE-2015-8104 and lock
up the CPU entirely.
CVSS Score
5.5
EPSS Score
0.001
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
x86 shadow plus log-dirty mode use-after-free In environments where host assisted address translation is necessary but Hardware Assisted Paging (HAP) is unavailable, Xen will run guests in so called shadow mode. Shadow mode maintains a pool of memory used for both shadow page tables as well as auxiliary data structures. To migrate or snapshot guests, Xen additionally runs them in so called log-dirty mode. The data structures needed by the log-dirty tracking are part of aformentioned auxiliary data. In order to keep error handling efforts within reasonable bounds, for operations which may require memory allocations shadow mode logic ensures up front that enough memory is available for the worst case requirements. Unfortunately, while page table memory is properly accounted for on the code path requiring the potential establishing of new shadows, demands by the log-dirty infrastructure were not taken into consideration. As a result, just established shadow page tables could be freed again immediately, while other code is still accessing them on the assumption that they would remain allocated.
CVSS Score
7.8
EPSS Score
0.0
Published
2023-03-21
Oxenstored 32->31 bit integer truncation issues Integers in Ocaml are 63 or 31 bits of signed precision. The Ocaml Xenbus library takes a C uint32_t out of the ring and casts it directly to an Ocaml integer. In 64-bit Ocaml builds this is fine, but in 32-bit builds, it truncates off the most significant bit, and then creates unsigned/signed confusion in the remainder. This in turn can feed a negative value into logic not expecting a negative value, resulting in unexpected exceptions being thrown. The unexpected exception is not handled suitably, creating a busy-loop trying (and failing) to take the bad packet out of the xenstore ring.
CVSS Score
5.5
EPSS Score
0.0
Published
2022-11-01
Xenstore: Guests can create arbitrary number of nodes via transactions T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] In case a node has been created in a transaction and it is later deleted in the same transaction, the transaction will be terminated with an error. As this error is encountered only when handling the deleted node at transaction finalization, the transaction will have been performed partially and without updating the accounting information. This will enable a malicious guest to create arbitrary number of nodes.
CVSS Score
5.5
EPSS Score
0.0
Published
2022-11-01
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