Commit 08da44ae authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini

KVM: x86: Decoding guest instructions which cross page boundary may fail

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.

Cc: stable@vger.kernel.org
Fixes: 5cfc7e0fSigned-off-by: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2bc19dc3
......@@ -778,8 +778,10 @@ static int __do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt, int op_size)
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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