| From bippy-7c5fe7eed585 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2025-21779: KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| KVM: x86: Reject Hyper-V's SEND_IPI hypercalls if local APIC isn't in-kernel |
| |
| Advertise support for Hyper-V's SEND_IPI and SEND_IPI_EX hypercalls if and |
| only if the local API is emulated/virtualized by KVM, and explicitly reject |
| said hypercalls if the local APIC is emulated in userspace, i.e. don't rely |
| on userspace to opt-in to KVM_CAP_HYPERV_ENFORCE_CPUID. |
| |
| Rejecting SEND_IPI and SEND_IPI_EX fixes a NULL-pointer dereference if |
| Hyper-V enlightenments are exposed to the guest without an in-kernel local |
| APIC: |
| |
| dump_stack+0xbe/0xfd |
| __kasan_report.cold+0x34/0x84 |
| kasan_report+0x3a/0x50 |
| __apic_accept_irq+0x3a/0x5c0 |
| kvm_hv_send_ipi.isra.0+0x34e/0x820 |
| kvm_hv_hypercall+0x8d9/0x9d0 |
| kvm_emulate_hypercall+0x506/0x7e0 |
| __vmx_handle_exit+0x283/0xb60 |
| vmx_handle_exit+0x1d/0xd0 |
| vcpu_enter_guest+0x16b0/0x24c0 |
| vcpu_run+0xc0/0x550 |
| kvm_arch_vcpu_ioctl_run+0x170/0x6d0 |
| kvm_vcpu_ioctl+0x413/0xb20 |
| __se_sys_ioctl+0x111/0x160 |
| do_syscal1_64+0x30/0x40 |
| entry_SYSCALL_64_after_hwframe+0x67/0xd1 |
| |
| Note, checking the sending vCPU is sufficient, as the per-VM irqchip_mode |
| can't be modified after vCPUs are created, i.e. if one vCPU has an |
| in-kernel local APIC, then all vCPUs have an in-kernel local APIC. |
| |
| The Linux kernel CVE team has assigned CVE-2025-21779 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.20 with commit 214ff83d4473a7757fa18a64dc7efe3b0e158486 and fixed in 5.10.236 with commit 61224533f2b61e252b03e214195d27d64b22989a |
| Issue introduced in 4.20 with commit 214ff83d4473a7757fa18a64dc7efe3b0e158486 and fixed in 5.15.179 with commit 45fa526b0f5a34492ed0536c3cdf88b78380e4de |
| Issue introduced in 4.20 with commit 214ff83d4473a7757fa18a64dc7efe3b0e158486 and fixed in 6.1.129 with commit 5393cf22312418262679eaadb130d608c75fe690 |
| Issue introduced in 4.20 with commit 214ff83d4473a7757fa18a64dc7efe3b0e158486 and fixed in 6.6.79 with commit 874ff13c73c45ecb38cb82191e8c1d523f0dc81b |
| Issue introduced in 4.20 with commit 214ff83d4473a7757fa18a64dc7efe3b0e158486 and fixed in 6.12.16 with commit aca8be4403fb90db7adaf63830e27ebe787a76e8 |
| Issue introduced in 4.20 with commit 214ff83d4473a7757fa18a64dc7efe3b0e158486 and fixed in 6.13.4 with commit ca29f58ca374c40a0e69c5306fc5c940a0069074 |
| Issue introduced in 4.20 with commit 214ff83d4473a7757fa18a64dc7efe3b0e158486 and fixed in 6.14 with commit a8de7f100bb5989d9c3627d3a223ee1c863f3b69 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2025-21779 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| arch/x86/kvm/hyperv.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/61224533f2b61e252b03e214195d27d64b22989a |
| https://git.kernel.org/stable/c/45fa526b0f5a34492ed0536c3cdf88b78380e4de |
| https://git.kernel.org/stable/c/5393cf22312418262679eaadb130d608c75fe690 |
| https://git.kernel.org/stable/c/874ff13c73c45ecb38cb82191e8c1d523f0dc81b |
| https://git.kernel.org/stable/c/aca8be4403fb90db7adaf63830e27ebe787a76e8 |
| https://git.kernel.org/stable/c/ca29f58ca374c40a0e69c5306fc5c940a0069074 |
| https://git.kernel.org/stable/c/a8de7f100bb5989d9c3627d3a223ee1c863f3b69 |
