From: Sean Christopherson <seanjc@google.com> stable inclusion from stable-v6.6.113 commit cd3efb93677c4b0cf76348882fb429165fee33fd category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/ID3WHO CVE: CVE-2025-40038 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 0910dd7c9ad45a2605c45fd2bf3d1bcac087687c ] Skip the WRMSR and HLT fastpaths in SVM's VM-Exit handler if the next RIP isn't valid, e.g. because KVM is running with nrips=false. SVM must decode and emulate to skip the instruction if the CPU doesn't provide the next RIP, and getting the instruction bytes to decode requires reading guest memory. Reading guest memory through the emulator can fault, i.e. can sleep, which is disallowed since the fastpath handlers run with IRQs disabled. BUG: sleeping function called from invalid context at ./include/linux/uaccess.h:106 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 32611, name: qemu preempt_count: 1, expected: 0 INFO: lockdep is turned off. irq event stamp: 30580 hardirqs last enabled at (30579): [<ffffffffc08b2527>] vcpu_run+0x1787/0x1db0 [kvm] hardirqs last disabled at (30580): [<ffffffffb4f62e32>] __schedule+0x1e2/0xed0 softirqs last enabled at (30570): [<ffffffffb4247a64>] fpu_swap_kvm_fpstate+0x44/0x210 softirqs last disabled at (30568): [<ffffffffb4247a64>] fpu_swap_kvm_fpstate+0x44/0x210 CPU: 298 UID: 0 PID: 32611 Comm: qemu Tainted: G U 6.16.0-smp--e6c618b51cfe-sleep #782 NONE Tainted: [U]=USER Hardware name: Google Astoria-Turin/astoria, BIOS 0.20241223.2-0 01/17/2025 Call Trace: <TASK> dump_stack_lvl+0x7d/0xb0 __might_resched+0x271/0x290 __might_fault+0x28/0x80 kvm_vcpu_read_guest_page+0x8d/0xc0 [kvm] kvm_fetch_guest_virt+0x92/0xc0 [kvm] __do_insn_fetch_bytes+0xf3/0x1e0 [kvm] x86_decode_insn+0xd1/0x1010 [kvm] x86_emulate_instruction+0x105/0x810 [kvm] __svm_skip_emulated_instruction+0xc4/0x140 [kvm_amd] handle_fastpath_invd+0xc4/0x1a0 [kvm] vcpu_run+0x11a1/0x1db0 [kvm] kvm_arch_vcpu_ioctl_run+0x5cc/0x730 [kvm] kvm_vcpu_ioctl+0x578/0x6a0 [kvm] __se_sys_ioctl+0x6d/0xb0 do_syscall_64+0x8a/0x2c0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f479d57a94b </TASK> Note, this is essentially a reapply of commit 5c30e8101e8d ("KVM: SVM: Skip WRMSR fastpath on VM-Exit if next RIP isn't valid"), but with different justification (KVM now grabs SRCU when skipping the instruction for other reasons). Fixes: b439eb8ab578 ("Revert "KVM: SVM: Skip WRMSR fastpath on VM-Exit if next RIP isn't valid"") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250805190526.1453366-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> [ adapted switch-based MSR/HLT fastpath to if-based MSR-only check ] Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: arch/x86/kvm/svm/svm.c [Context conflicts due to stable commit ca3cc405a3bc ("KVM: x86: Move handling of is_guest_mode() into fastpath exit handlers") not merged. Also this makes nrip check comes after is_guest_mode check, which is fine as both checks return the same exit code.] Signed-off-by: Pan Taixi <pantaixi1@huawei.com> --- arch/x86/kvm/svm/svm.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 8692b7892d0f..7bf68a753a97 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4206,8 +4206,17 @@ static int svm_vcpu_pre_run(struct kvm_vcpu *vcpu) static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu) { - if (to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_MSR && - to_svm(vcpu)->vmcb->control.exit_info_1) + struct vcpu_svm *svm = to_svm(vcpu); + + /* + * Next RIP must be provided as IRQs are disabled, and accessing guest + * memory to decode the instruction might fault, i.e. might sleep. + */ + if (!nrips || !svm->vmcb->control.next_rip) + return EXIT_FASTPATH_NONE; + + if (svm->vmcb->control.exit_code == SVM_EXIT_MSR && + svm->vmcb->control.exit_info_1) return handle_fastpath_set_msr_irqoff(vcpu); return EXIT_FASTPATH_NONE; -- 2.34.1