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CVE-2025-68810 — KVM: Disallow toggling KVM_MEM_GUEST_MEMFD on an existing memslot

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

KVM: Disallow toggling KVM_MEM_GUEST_MEMFD on an existing memslot

Reject attempts to disable KVM_MEM_GUEST_MEMFD on a memslot that was initially created with a guest_memfd binding, as KVM doesn't support toggling KVM_MEM_GUEST_MEMFD on existing memslots. KVM prevents enabling KVM_MEM_GUEST_MEMFD, but doesn't prevent clearing the flag.

Failure to reject the new memslot results in a use-after-free due to KVM not unbinding from the guest_memfd instance. Unbinding on a FLAGS_ONLY change is easy enough, and can/will be done as a hardening measure (in anticipation of KVM supporting dirty logging on guest_memfd at some point), but fixing the use-after-free would only address the immediate symptom.

================================================================== BUG: KASAN: slab-use-after-free in kvm_gmem_release+0x362/0x400 [kvm] Write of size 8 at addr ffff8881111ae908 by task repro/745

CPU: 7 UID: 1000 PID: 745 Comm: repro Not tainted 6.18.0-rc6-115d5de2eef3-next-kasan #3 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: <TASK> dump_stack_lvl+0x51/0x60 print_report+0xcb/0x5c0 kasan_report+0xb4/0xe0 kvm_gmem_release+0x362/0x400 [kvm] __fput+0x2fa/0x9d0 task_work_run+0x12c/0x200 do_exit+0x6ae/0x2100 do_group_exit+0xa8/0x230 __x64_sys_exit_group+0x3a/0x50 x64_sys_call+0x737/0x740 do_syscall_64+0x5b/0x900 entry_SYSCAL…

USN-8177-1 — linux, linux-realtime vulnerabilities

Affected: Ubuntu:25.10: linux, Ubuntu:25.10: linux-realtime

Josh Eads, Kristoffer Janke, Eduardo Vela Nava, Tavis Ormandy, and Matteo Rizzo discovered that some AMD Zen processors did not properly verify the signature of CPU microcode. This flaw is known as EntrySign. A privileged attacker could possibly use this issue to cause load malicious CPU microcode causing loss of integrity and confidentiality. (CVE-2024-36347)

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - MIPS architecture; - PowerPC architecture; - User-Mode Linux (UML); - x86 architecture; - Block layer subsystem; - Cryptographic API; - ACPI drivers; - Ublk userspace block driver; - Bluetooth drivers; - Character device driver; - TPM device driver; - Clock framework and drivers; - GPU drivers; - Hardware monitoring drivers; - Intel Trace Hub HW tracing drivers; - InfiniBand drivers; - Input Device core drivers; - Input Device (Mouse) drivers; - IOMMU subsystem; - Multiple devices driver; - Media drivers; - Network drivers; - Mellanox network drivers; - STMicroelectronics network drivers; - Ethernet team driver; - PA-RISC drivers; - Chrome hardware platform drivers; - x86 platform drivers; - SCSI subsystem; - SPI subsystem; - TCM subsystem; - Freescale USB OTG Transceiver Driver; - USB Type-C Connector System Software Interface driver; - Watchdog drivers; - BTRFS file sy…