| Message ID | 20200323191243.30002-1-ndesaulniers@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: VMX: don't allow memory operands for inline asm that modifies SP | expand |
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 4d22b1b5e822..310e8c1169b8 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6277,7 +6277,7 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu) #endif ASM_CALL_CONSTRAINT : - THUNK_TARGET(entry), + [thunk_target]"r"(entry), [ss]"i"(__KERNEL_DS), [cs]"i"(__KERNEL_CS) );
THUNK_TARGET defines [thunk_target] as having "rm" input constraints when CONFIG_RETPOLINE is not set, which isn't constrained enough for this specific case. For inline assembly that modifies the stack pointer before using this input, the underspecification of constraints is dangerous, and results in an indirect call to a previously pushed flags register. In this case `entry`'s stack slot is good enough to satisfy the "m" constraint in "rm", but the inline assembly in handle_external_interrupt_irqoff() modifies the stack pointer via push+pushf before using this input, which in this case results in calling what was the previous state of the flags register, rather than `entry`. Be more specific in the constraints by requiring `entry` be in a register, and not a memory operand. Reported-by: Dmitry Vyukov <dvyukov@google.com> Reported-by: syzbot+3f29ca2efb056a761e38@syzkaller.appspotmail.com Debugged-by: Alexander Potapenko <glider@google.com> Debugged-by: Paolo Bonzini <pbonzini@redhat.com> Debugged-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- arch/x86/kvm/vmx/vmx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)