From: Yosry Ahmed Date: Mon, 16 Mar 2026 20:27:24 +0000 (+0000) Subject: KVM: SVM: Properly check RAX in the emulator for SVM instructions X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c85aaff26d55920d783adac431a59ec738a35aef;p=thirdparty%2Fkernel%2Fstable.git KVM: SVM: Properly check RAX in the emulator for SVM instructions Architecturally, VMRUN/VMLOAD/VMSAVE should generate a #GP if the physical address in RAX is not supported. check_svme_pa() hardcodes this to checking that bits 63-48 are not set. This is incorrect on HW supporting 52 bits of physical address space. Additionally, the emulator does not check if the address is not aligned, which should also result in #GP. Use page_address_valid() which properly checks alignment and the address legality based on the guest's MAXPHYADDR. Plumb it through x86_emulate_ops, similar to is_canonical_addr(), to avoid directly accessing the vCPU object in emulator code. Fixes: 01de8b09e606 ("KVM: SVM: Add intercept checks for SVM instructions") Suggested-by: Sean Christopherson Signed-off-by: Yosry Ahmed Link: https://patch.msgid.link/20260316202732.3164936-2-yosry@kernel.org Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c8e292e9a24d..202c376ff501 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3874,8 +3874,7 @@ static int check_svme_pa(struct x86_emulate_ctxt *ctxt) { u64 rax = reg_read(ctxt, VCPU_REGS_RAX); - /* Valid physical address? */ - if (rax & 0xffff000000000000ULL) + if (!ctxt->ops->page_address_valid(ctxt, rax)) return emulate_gp(ctxt, 0); return check_svme(ctxt); diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h index fb3dab4b5a53..0abff36d0994 100644 --- a/arch/x86/kvm/kvm_emulate.h +++ b/arch/x86/kvm/kvm_emulate.h @@ -245,6 +245,8 @@ struct x86_emulate_ops { bool (*is_canonical_addr)(struct x86_emulate_ctxt *ctxt, gva_t addr, unsigned int flags); + + bool (*page_address_valid)(struct x86_emulate_ctxt *ctxt, gpa_t gpa); }; /* Type, address-of, and value of an instruction's operand. */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index aa29f90c6e96..2410401c57d8 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8907,6 +8907,11 @@ static bool emulator_is_canonical_addr(struct x86_emulate_ctxt *ctxt, return !is_noncanonical_address(addr, emul_to_vcpu(ctxt), flags); } +static bool emulator_page_address_valid(struct x86_emulate_ctxt *ctxt, gpa_t gpa) +{ + return page_address_valid(emul_to_vcpu(ctxt), gpa); +} + static const struct x86_emulate_ops emulate_ops = { .vm_bugged = emulator_vm_bugged, .read_gpr = emulator_read_gpr, @@ -8954,6 +8959,7 @@ static const struct x86_emulate_ops emulate_ops = { .set_xcr = emulator_set_xcr, .get_untagged_addr = emulator_get_untagged_addr, .is_canonical_addr = emulator_is_canonical_addr, + .page_address_valid = emulator_page_address_valid, }; static void toggle_interruptibility(struct kvm_vcpu *vcpu, u32 mask)