From e4c91a3f90d678490fb6c88e7e79142a4b18d854 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 26 Jul 2012 16:57:18 +0100 Subject: x86/hvm: don't leave emulator in inconsistent state The fact that handle_mmio(), and thus the instruction emulator, is being run through twice for emulations that require involvement of the device model, allows for the second run to see a different guest state than the first one. Since only the MMIO-specific emulation routines update the vCPU's io_state, if they get invoked on the second pass, internal state (and particularly this variable) can be left in a state making successful emulation of a subsequent MMIO operation impossible. Consequently, whenever the emulator invocation returns without requesting a retry of the guest instruction, reset io_state. [ This is a security issue. XSA#10. -iwj ] Signed-off-by: Jan Beulich Acked-by: Keir Fraser Committed-by: Ian Jackson xen-unstable changeset: 25682:ffcb24876b4f Committed-by: Ian Jackson --- xen/arch/x86/hvm/io.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c index 3c31a6d2e4..d59c237f78 100644 --- a/xen/arch/x86/hvm/io.c +++ b/xen/arch/x86/hvm/io.c @@ -176,6 +176,8 @@ int handle_mmio(void) rc = hvm_emulate_one(&ctxt); + if ( rc != X86EMUL_RETRY ) + curr->arch.hvm_vcpu.io_state = HVMIO_none; if ( curr->arch.hvm_vcpu.io_state == HVMIO_awaiting_completion ) curr->arch.hvm_vcpu.io_state = HVMIO_handle_mmio_awaiting_completion; else -- cgit v1.2.3