3.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
commit 08da44aedba0f493e10695fa334348a7a4f72eb3 upstream.
Once an instruction crosses a page boundary, the size read from the second page
disregards the common case that part of the operand resides on the first page.
As a result, fetch of long insturctions may fail, and thereby cause the
decoding to fail as well.
Fixes: 5cfc7e0f5e5e1adf998df94f8e36edaf5d30d38e
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -773,8 +773,10 @@ static int __do_insn_fetch_bytes(struct
static __always_inline int do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt,
unsigned size)
{
- if (unlikely(ctxt->fetch.end - ctxt->fetch.ptr < size))
- return __do_insn_fetch_bytes(ctxt, size);
+ unsigned done_size = ctxt->fetch.end - ctxt->fetch.ptr;
+
+ if (unlikely(done_size < size))
+ return __do_insn_fetch_bytes(ctxt, size - done_size);
else
return X86EMUL_CONTINUE;
}
--
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