From 2fc1d9e84b41295c4529235e854f1ac4e6d2d840 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 19 Feb 2021 16:41:03 +0800 Subject: [PATCH] KVM: x86: Update emulator context mode if SYSENTER xfers to 64-bit mode stable inclusion from stable-5.10.15 commit d73af5ae22d419264208a5411cfaf5b3ccb1bd48 bugzilla: 48167 -------------------------------- commit 943dea8af21bd896e0d6c30ea221203fb3cd3265 upstream. Set the emulator context to PROT64 if SYSENTER transitions from 32-bit userspace (compat mode) to a 64-bit kernel, otherwise the RIP update at the end of x86_emulate_insn() will incorrectly truncate the new RIP. Note, this bug is mostly limited to running an Intel virtual CPU model on an AMD physical CPU, as other combinations of virtual and physical CPUs do not trigger full emulation. On Intel CPUs, SYSENTER in compatibility mode is legal, and unconditionally transitions to 64-bit mode. On AMD CPUs, SYSENTER is illegal in compatibility mode and #UDs. If the vCPU is AMD, KVM injects a #UD on SYSENTER in compat mode. If the pCPU is Intel, SYSENTER will execute natively and not trigger #UD->VM-Exit (ignoring guest TLB shenanigans). Fixes: fede8076aab4 ("KVM: x86: handle wrap around 32-bit address space") Cc: stable@vger.kernel.org Signed-off-by: Jonny Barker [sean: wrote changelog] Signed-off-by: Sean Christopherson Message-Id: <20210202165546.2390296-1-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman Signed-off-by: Zheng Zengkai Acked-by: Xie XiuQi --- arch/x86/kvm/emulate.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 56cae1ff9e3f..66a08322988f 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2879,6 +2879,8 @@ static int em_sysenter(struct x86_emulate_ctxt *ctxt) ops->get_msr(ctxt, MSR_IA32_SYSENTER_ESP, &msr_data); *reg_write(ctxt, VCPU_REGS_RSP) = (efer & EFER_LMA) ? msr_data : (u32)msr_data; + if (efer & EFER_LMA) + ctxt->mode = X86EMUL_MODE_PROT64; return X86EMUL_CONTINUE; } -- GitLab