# HG changeset patch
# User Jan Beulich <jbeulich@suse.com>
# Date 1343318195 -3600
# Node ID a43f5b4b03319117edba76ebca8f827119d4e9a8
# Parent e89be0dedeb4e4a9556cf3e1b9a5295ba0b59edf
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 <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
xen-unstable changeset: 25682:ffcb24876b4f
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
diff -r e89be0dedeb4 -r a43f5b4b0331 xen/arch/x86/hvm/io.c
--- a/xen/arch/x86/hvm/io.c Sun Jul 22 16:39:00 2012 +0100
+++ b/xen/arch/x86/hvm/io.c Thu Jul 26 16:56:35 2012 +0100
@@ -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