kernel/linux.git/arch/x86, branch v6.18.44

KVM: SVM: Update x2APIC MSR intercepts if AVIC is inhibited while L2 is active

2026-08-09T18:25:11+00:00

commit 7d3aae206663c4e006b25a1c7a20a4029e67da76 upstream. Always update x2APIC MSR intercepts for L1 when AVIC is deactivated, even if L2 is active and KVM is using a separate MSR bitmap to run L2. If AVIC is fully enabled prior to running L2, and is then inhibited while L2 is active (for a VM-scoped inhibit), then KVM will run L1 with AVIC disabled, but with x2APIC MSR intercepts disabled, i.e. will allow L1 to read most of the host's APIC state, send arbitrary interrupts, change task priority, and ultimately trivially DoS the host. E.g. sending a self-IPI in L1 on HYPERV_REENLIGHTENMENT_VECTOR, 0xee, with CONFIG_HYPERV=n in the host kernel as a "safe" PoC, yields: Spurious interrupt (vector 0xee) on CPU#425. Acked And hacking KVM to abuse kvm_set_posted_intr_wakeup_handler() to register a handler and WARN on POSTED_INTR_WAKEUP_VECTOR yields: ------------[ cut here ]------------ WARNING: arch/x86/kvm/svm/svm.c:5594 at pi_wakeup_handler+0x9/0x10 [kvm_amd], CPU#156: nested_x2apic_t/316940 CPU: 156 UID: 0 PID: 316940 Comm: nested_x2apic_t Tainted: G S U Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER Hardware name: Google Astoria-Turin/astoria, BIOS 0.20260209.0-0 02/09/2026 RIP: 0010:pi_wakeup_handler+0x9/0x10 [kvm_amd] Call Trace: sysvec_kvm_posted_intr_wakeup_ipi+0x64/0x80 asm_sysvec_kvm_posted_intr_wakeup_ipi+0x1a/0x20 RIP: 0010:vcpu_run+0x1430/0x1e40 [kvm] kvm_arch_vcpu_ioctl_run+0x2c1/0x600 [kvm] kvm_vcpu_ioctl+0x580/0x6b0 [kvm] __se_sys_ioctl+0x6d/0xb0 do_syscall_64+0x10a/0x480 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x46ff4b ---[ end trace 0000000000000000 ]--- Fixes: 091abbf578f9 ("KVM: x86: nSVM: optimize svm_set_x2apic_msr_interception") Cc: stable@vger.kernel.org Cc: Yosry Ahmed Signed-off-by: Sean Christopherson Link: https://patch.msgid.link/20260729213558.639074-1-pbonzini@redhat.com/ Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

KVM: VMX: add memory clobber to asm for VMX instructions

2026-08-09T18:25:11+00:00

commit 0e65cd9e5d41c34f86b7c347967bedac54926041 upstream. VMCLEAR/VMREAD/VMWRITE/VMPTRLD access the internal VMCS cache, which is not visible to the compiler; without a memory clobber, the compiler can reorder them in troublesome ways because "asm volatile" and "asm goto" only protect against removal of the asm. For example, placing a VMWRITE before the corresponding VMCS pointer is loaded can lead to corruption. While none of this has been observed, it is better to prevent than cure. Likewise, INVEPT and INVVPID access the TLB and, even though in their case the effect is only visible to the next VMLAUNCH/VMRESUME, it is technically correct to add the clobber there too. So avoid any urge to special case them, and simply hardcode "memory" into the clobber list of vmx_asm1() and vmx_asm2(). __vmcs_readl() open-codes its own asm, so add the clobber there as well. Link: https://lore.kernel.org/kvm/CABgObfbL3t21yVeSwiLSjjOUER+rTYDPHYAH9YU4TWGRjx6XHg@mail.gmail.com/ Cc: Sean Christopherson Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

x86/boot: Add volatile, clobbers and zero-length test in memcmp()

2026-08-09T18:25:07+00:00

[ Upstream commit a8c171c107c0b61a5e7e10cedab0fb72aeaf640d ] Add the volatile qualifier and clobbers parameter to prevent bugs with instruction reordering and optimization. Also add TEST for the zero-length case to set ZF, as, if the count register is zero, the REPE prefix does not run the CMPSB instruction, leaving the ZF flag undetermined. [ bp: Add a comment about the len==0 case. ] Fixes: 62bd0337d0c4 ("Top header file for new x86 setup code") Closes: https://sashiko.dev/#/patchset/20260701-pvh-kasan-inline-v6-0-ba99045dfa9f%40igalia.com Suggested-by: Borislav Petkov Signed-off-by: Mauricio Faria de Oliveira Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/all/20260721-pvh-kasan-inline-v7-2-38979a50cef0@igalia.com Signed-off-by: Sasha Levin

arch/x86: mshyperv: Discover Confidential VMBus availability

2026-08-09T18:25:00+00:00

[ Upstream commit 7c8b6c326d830ca5c6b95f390c703966e14167e6 ] Confidential VMBus requires enabling paravisor SynIC, and the x86_64 guest has to inspect the Virtualization Stack (VS) CPUID leaf to see if Confidential VMBus is available. If it is, the guest shall enable the paravisor SynIC. Read the relevant data from the VS CPUID leaf. Refactor the code to avoid repeating CPUID and add flags to the struct ms_hyperv_info. For ARM64, the flag for Confidential VMBus is not set which provides the desired behaviour for now as it is not available on ARM64 just yet. Once ARM64 CCA guests are supported, this flag will be set unconditionally when running such a guest. Signed-off-by: Roman Kisel Reviewed-by: Michael Kelley Signed-off-by: Wei Liu Stable-dep-of: 8c7ab779c885 ("Drivers: hv: vmbus: Replace lockdep_hardirq_threaded() with lockdep annotation") Signed-off-by: Sasha Levin

x86/bugs: Make Safe-RET robust against interrupt injection

2026-08-06T17:27:09+00:00

commit 7e7f81cf6f5ca3311e526308f55d7c54d3ba71f9 upstream. An attacker injecting interrupts while the Safe-RET mitigation executes on machines affected by SRSO can neutralize the safe return sequence, potentially leading to data leakage through speculative execution. Fixup register state as if the Safe-RET sequence executed successfully by "emulating" it, in a manner of speaking, and avoid executing a RET instruction after returning from the interrupt. Co-developed-by: David Kaplan Signed-off-by: David Kaplan Signed-off-by: Borislav Petkov (AMD) Signed-off-by: Greg Kroah-Hartman

KVM: SVM: Bump asid_generation on CPU online to avoid ASID collision after hotplug

2026-08-03T09:22:13+00:00

commit 25f744ffa0c8e799e06250ce2e618367b166b0d4 upstream. If a vCPU stays scheduled out (or blocked) while the last pCPU it ran on goes through a hotplug cycle (online->offline->online), and the vCPU then resumes execution on the same pCPU, then it is possible for it to run with an ASID that has now been assigned to a different vCPU, resulting in stale TLB translations being used. svm_enable_virtualization_cpu() resets asid_generation to 1 and sets next_asid to max_asid + 1 on every CPU online event, including hotplug cycles. Because next_asid starts beyond the pool boundary, the first call to new_asid() after an online event always wraps the pool, incrementing asid_generation to 2 and assigning ASIDs starting from min_asid. Consider two vCPUs from different VMs, vCPU-A pinned to CPU-X holding asid_generation=2 and ASID=N from before the hotplug event: 1. CPU-X goes offline and back online: asid_generation resets to 1, next_asid = max_asid + 1. 2. One or more vCPUs migrate to CPU-X and call new_asid(), wrapping the pool and consuming ASIDs starting from min_asid. Eventually vCPU-B from a different VM is assigned asid_generation=2, ASID=N — the same ASID that vCPU-A held before the hotplug. 3. vCPU-A enters pre_svm_run() on CPU-X: current_vmcb->cpu is unchanged so the migration branch is skipped. Its saved asid_generation=2 matches sd->asid_generation=2, so the generation check silently passes and vCPU-A continues running with ASID=N — the same ASID just freshly assigned to vCPU-B. Both vCPUs from different VMs now run on CPU-X with the same ASID, causing them to share NPT TLB entries and producing stale translations. The collision manifests as a KVM internal error (Suberror: 1, emulation failure). The NPT page fault reports a faulting GPA far outside the VM's physical memory range — a sign of stale TLB translations being used. KVM falls back to instruction emulation, which fails on FPU/XSave instructions (XRSTOR, STMXCSR) that the emulator does not implement. Fix this by incrementing asid_generation instead of resetting it to 1 in svm_enable_virtualization_cpu(). On module load, asid_generation starts at 0 (memset) and the increment produces 1, identical to the old behaviour. On subsequent hotplug cycles the generation advances beyond any value a vCPU previously observed on this CPU, so the generation check in pre_svm_run() reliably forces new_asid() on every vCPU after every hotplug cycle. Fixes: 774c47f1d78e ("[PATCH] KVM: cpu hotplug support") Reported-by: Chandrakanth Silveru Tested-by: Srikanth Aithal Reviewed-by: K Prateek Nayak Reviewed-by: Tom Lendacky Signed-off-by: Nikunj A Dadhania Message-ID: <20260715063506.672432-1-nikunj@amd.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

x86,fs/resctrl: Rename some L3 specific functions

2026-08-03T09:22:11+00:00

[ Upstream commit 9c214d10c50990c7a61b95887493df9ae713eec5 ] With the arrival of monitor events tied to new domains associated with a different resource it would be clearer if the L3 resource specific functions are more accurately named. Rename three groups of functions: Functions that allocate/free architecture per-RMID MBM state information: arch_domain_mbm_alloc() -> l3_mon_domain_mbm_alloc() mon_domain_free() -> l3_mon_domain_free() Functions that allocate/free filesystem per-RMID MBM state information: domain_setup_mon_state() -> domain_setup_l3_mon_state() domain_destroy_mon_state() -> domain_destroy_l3_mon_state() Initialization/exit: rdt_get_mon_l3_config() -> rdt_get_l3_mon_config() resctrl_mon_resource_init() -> resctrl_l3_mon_resource_init() resctrl_mon_resource_exit() -> resctrl_l3_mon_resource_exit() Ensure kernel-doc descriptions of these functions' return values are present and correctly formatted. Signed-off-by: Tony Luck Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Reinette Chatre Link: https://lore.kernel.org/20251217172121.12030-1-tony.luck@intel.com Stable-dep-of: 52fce648607e ("fs/resctrl: Fix use-after-free during unmount") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

x86,fs/resctrl: Rename struct rdt_mon_domain and rdt_hw_mon_domain

2026-08-03T09:22:11+00:00

[ Upstream commit 4bc3ef46ff41d5e7ba557e56e9cd2031527cd7f8 ] The upcoming telemetry event monitoring is not tied to the L3 resource and will have a new domain structure. Rename the L3 resource specific domain data structures to include "l3_" in their names to avoid confusion between the different resource specific domain structures: rdt_mon_domain -> rdt_l3_mon_domain rdt_hw_mon_domain -> rdt_hw_l3_mon_domain No functional change. Signed-off-by: Tony Luck Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Reinette Chatre Link: https://lore.kernel.org/20251217172121.12030-1-tony.luck@intel.com Stable-dep-of: 52fce648607e ("fs/resctrl: Fix use-after-free during unmount") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

x86/boot/compressed: Disable jump tables

2026-08-03T09:21:59+00:00

commit 4a9ec5ec9555ad62dc5b81a37ac946025c2ea002 upstream. After a recent upstream LLVM change to start generating jump and lookup tables in switch statements in more instances [1], linking the compressed x86 boot image when CONFIG_KERNEL_ZSTD is enabled fails with: ld.lld: error: Unexpected run-time relocations (.rela) detected! Dumping the relocations in misc.o, which is the only file influenced by CONFIG_KERNEL_ZSTD in the decompressor, shows dynamic relocations to some string constants, which correspond to the string literals in the switch statement in handle_zstd_error(): Relocation section '.rela.data.rel.ro' at offset 0x277b0 contains 31 entries: Offset Info Type Symbol's Value Symbol's Name + Addend 0000000000000000 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 73a 0000000000000008 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e 0000000000000010 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e 0000000000000018 0000006600000001 R_X86_64_64 0000000000000000 .rodata.str1.1 + 78e ... This optimization is problematic for the decompressor environment, as it is built as -fPIE without any explicit absolute references (as described at the top of misc.c) while not applying any dynamic relocations, hence the linker assertion. To opt out of this optimization, which is of little value in this special early boot code, and to mirror the other x86 startup code in arch/x86/boot/startup, disable jump tables in the decompressor. Signed-off-by: Nathan Chancellor Signed-off-by: Ingo Molnar Acked-by: Ard Biesheuvel Cc: Bill Wendling Cc: Justin Stitt Cc: Nick Desaulniers Cc: "H. Peter Anvin" Cc: Peter Zijlstra Cc: stable@vger.kernel.org Link: https://github.com/llvm/llvm-project/commit/fa02a6ed66b1700c996b49c96c6bc0eb014c9518 [1] Link: https://patch.msgid.link/20260722-x86-boot-compressed-disable-jt-clang-v2-1-7373d38482fb@kernel.org Closes: https://github.com/ClangBuiltLinux/linux/issues/2165 Signed-off-by: Greg Kroah-Hartman

KVM: x86/mmu: Fix use-after-free on vendor module reload

2026-08-03T09:21:26+00:00

commit 52f2f7c30126037975389aa04d24c506a5177c35 upstream. mmu_destroy_caches() destroys pte_list_desc_cache and mmu_page_header_cache, but leaves both pointers unchanged. The pointers live in kvm.ko, and therefore survive when a vendor module is unloaded while kvm.ko remains loaded. If creation of pte_list_desc_cache fails during a subsequent vendor module load, its assignment sets pte_list_desc_cache to NULL and the error path calls mmu_destroy_caches(). mmu_page_header_cache still points to the cache destroyed during the preceding vendor module unload. Passing that stale pointer to kmem_cache_destroy() causes a slab use-after-free. Reproduce the issue on a v7.1.3 kernel with CONFIG_KASAN=y, CONFIG_KASAN_GENERIC=y, CONFIG_KVM=m, and CONFIG_KVM_INTEL=m. A one-shot test hook forces pte_list_desc_cache to NULL on the second invocation of kvm_mmu_vendor_module_init(): 1. Load kvm.ko and kvm-intel.ko, creating both caches. 2. Unload only kvm_intel, leaving kvm.ko loaded. 3. Reload kvm_intel and force initialization through the -ENOMEM path. KASAN reports: BUG: KASAN: slab-use-after-free in kvm_mmu_vendor_module_init+0x5b/0x170 [kvm] ... kmem_cache_destroy+0x21/0x1d0 kvm_mmu_vendor_module_init+0x5b/0x170 [kvm] ... Allocated by task 16817: __kmem_cache_create_args+0x12c/0x3b0 __kmem_cache_create.constprop.0+0xb6/0xf0 [kvm] kvm_mmu_vendor_module_init+0x13b/0x170 [kvm] ... Freed by task 16820: kmem_cache_destroy+0x117/0x1d0 kvm_mmu_vendor_module_exit+0x21/0x30 [kvm] Clear both pointers immediately after destroying their caches so that the stored state reflects the caches' lifetime and repeated cleanup is safe. With the fix applied, the same injected vendor module reload fails with -ENOMEM as expected and produces no KASAN report. Fixes: cb498ea2ce1d ("KVM: Portability: Combine kvm_init and kvm_init_x86") Cc: stable@vger.kernel.org Signed-off-by: Phil Rosenthal Message-ID: <20260718-kvm-mmu-cache-uaf-v3-1-e103b93c74e1@phil.gs> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman