| From 35b36871c0edb922981c217e2cb1f7529bc2c478 Mon Sep 17 00:00:00 2001 |
| From: Wanpeng Li <wanpengli@tencent.com> |
| Date: Wed, 18 Sep 2019 17:50:10 +0800 |
| Subject: [PATCH] KVM: X86: Fix userspace set invalid CR4 |
| |
| commit 3ca94192278ca8de169d78c085396c424be123b3 upstream. |
| |
| Reported by syzkaller: |
| |
| WARNING: CPU: 0 PID: 6544 at /home/kernel/data/kvm/arch/x86/kvm//vmx/vmx.c:4689 handle_desc+0x37/0x40 [kvm_intel] |
| CPU: 0 PID: 6544 Comm: a.out Tainted: G OE 5.3.0-rc4+ #4 |
| RIP: 0010:handle_desc+0x37/0x40 [kvm_intel] |
| Call Trace: |
| vmx_handle_exit+0xbe/0x6b0 [kvm_intel] |
| vcpu_enter_guest+0x4dc/0x18d0 [kvm] |
| kvm_arch_vcpu_ioctl_run+0x407/0x660 [kvm] |
| kvm_vcpu_ioctl+0x3ad/0x690 [kvm] |
| do_vfs_ioctl+0xa2/0x690 |
| ksys_ioctl+0x6d/0x80 |
| __x64_sys_ioctl+0x1a/0x20 |
| do_syscall_64+0x74/0x720 |
| entry_SYSCALL_64_after_hwframe+0x49/0xbe |
| |
| When CR4.UMIP is set, guest should have UMIP cpuid flag. Current |
| kvm set_sregs function doesn't have such check when userspace inputs |
| sregs values. SECONDARY_EXEC_DESC is enabled on writes to CR4.UMIP |
| in vmx_set_cr4 though guest doesn't have UMIP cpuid flag. The testcast |
| triggers handle_desc warning when executing ltr instruction since |
| guest architectural CR4 doesn't set UMIP. This patch fixes it by |
| adding valid CR4 and CPUID combination checking in __set_sregs. |
| |
| syzkaller source: https://syzkaller.appspot.com/x/repro.c?x=138efb99600000 |
| |
| Reported-by: syzbot+0f1819555fbdce992df9@syzkaller.appspotmail.com |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Wanpeng Li <wanpengli@tencent.com> |
| Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> |
| Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c |
| index 2c118c9da16c..5c6f2580e85e 100644 |
| --- a/arch/x86/kvm/x86.c |
| +++ b/arch/x86/kvm/x86.c |
| @@ -879,34 +879,42 @@ int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr) |
| } |
| EXPORT_SYMBOL_GPL(kvm_set_xcr); |
| |
| -int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) |
| +static int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) |
| { |
| - unsigned long old_cr4 = kvm_read_cr4(vcpu); |
| - unsigned long pdptr_bits = X86_CR4_PGE | X86_CR4_PSE | X86_CR4_PAE | |
| - X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_PKE; |
| - |
| if (cr4 & CR4_RESERVED_BITS) |
| - return 1; |
| + return -EINVAL; |
| |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && (cr4 & X86_CR4_OSXSAVE)) |
| - return 1; |
| + return -EINVAL; |
| |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_SMEP) && (cr4 & X86_CR4_SMEP)) |
| - return 1; |
| + return -EINVAL; |
| |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_SMAP) && (cr4 & X86_CR4_SMAP)) |
| - return 1; |
| + return -EINVAL; |
| |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_FSGSBASE) && (cr4 & X86_CR4_FSGSBASE)) |
| - return 1; |
| + return -EINVAL; |
| |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_PKU) && (cr4 & X86_CR4_PKE)) |
| - return 1; |
| + return -EINVAL; |
| |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_LA57) && (cr4 & X86_CR4_LA57)) |
| - return 1; |
| + return -EINVAL; |
| |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_UMIP) && (cr4 & X86_CR4_UMIP)) |
| + return -EINVAL; |
| + |
| + return 0; |
| +} |
| + |
| +int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) |
| +{ |
| + unsigned long old_cr4 = kvm_read_cr4(vcpu); |
| + unsigned long pdptr_bits = X86_CR4_PGE | X86_CR4_PSE | X86_CR4_PAE | |
| + X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_PKE; |
| + |
| + if (kvm_valid_cr4(vcpu, cr4)) |
| return 1; |
| |
| if (is_long_mode(vcpu)) { |
| @@ -8546,10 +8554,6 @@ EXPORT_SYMBOL_GPL(kvm_task_switch); |
| |
| static int kvm_valid_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs) |
| { |
| - if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && |
| - (sregs->cr4 & X86_CR4_OSXSAVE)) |
| - return -EINVAL; |
| - |
| if ((sregs->efer & EFER_LME) && (sregs->cr0 & X86_CR0_PG)) { |
| /* |
| * When EFER.LME and CR0.PG are set, the processor is in |
| @@ -8568,7 +8572,7 @@ static int kvm_valid_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs) |
| return -EINVAL; |
| } |
| |
| - return 0; |
| + return kvm_valid_cr4(vcpu, sregs->cr4); |
| } |
| |
| static int __set_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs) |
| -- |
| 2.7.4 |
| |