From: Wanpeng Li <[email protected]>
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 check
for guest UMIP cpuid flag when get sreg inputs from userspace.
Reported-by: [email protected]
Fixes: 0367f205a3b7 ("KVM: vmx: add support for emulating UMIP")
Cc: [email protected]
Signed-off-by: Wanpeng Li <[email protected]>
---
Note: syzbot report link https://lkml.org/lkml/2019/9/11/799
arch/x86/kvm/x86.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f7cfd8e..83288ba 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8645,6 +8645,10 @@ static int kvm_valid_sregs(struct kvm_vcpu *vcpu, struct
kvm_sregs *sregs)
(sregs->cr4 & X86_CR4_OSXSAVE))
return -EINVAL;
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_UMIP) &&
+ (sregs->cr4 & X86_CR4_UMIP))
+ return -EINVAL;
+
if ((sregs->efer & EFER_LME) && (sregs->cr0 & X86_CR0_PG)) {
/*
* When EFER.LME and CR0.PG are set, the processor is in
--
2.7.4
