From: Steve Rutherford <[email protected]>
commit 129a72a0d3c8e139a04512325384fe5ac119e74d upstream.
Introduces segemented_write_std.
Switches from emulated reads/writes to standard read/writes in fxsave,
fxrstor, sgdt, and sidt. This fixes CVE-2017-2584, a longstanding
kernel memory leak.
Since commit 283c95d0e389 ("KVM: x86: emulate FXSAVE and FXRSTOR",
2016-11-09), which is luckily not yet in any final release, this would
also be an exploitable kernel memory *write*!
Reported-by: Dmitry Vyukov <[email protected]>
Fixes: 96051572c819194c37a8367624b285be10297eca
Fixes: 283c95d0e3891b64087706b344a4b545d04a6e62
Suggested-by: Paolo Bonzini <[email protected]>
Signed-off-by: Steve Rutherford <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Signed-off-by: Willy Tarreau <[email protected]>
---
arch/x86/kvm/emulate.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 364f020..c964850 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -906,6 +906,20 @@ static int segmented_read_std(struct x86_emulate_ctxt
*ctxt,
return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception);
}
+static int segmented_write_std(struct x86_emulate_ctxt *ctxt,
+ struct segmented_address addr,
+ void *data,
+ unsigned int size)
+{
+ int rc;
+ ulong linear;
+
+ rc = linearize(ctxt, addr, size, true, &linear);
+ if (rc != X86EMUL_CONTINUE)
+ return rc;
+ return ctxt->ops->write_std(ctxt, linear, data, size, &ctxt->exception);
+}
+
/*
* Fetch the next byte of the instruction being emulated which is pointed to
* by ctxt->_eip, then increment ctxt->_eip.
@@ -3361,8 +3375,8 @@ static int emulate_store_desc_ptr(struct x86_emulate_ctxt
*ctxt,
}
/* Disable writeback. */
ctxt->dst.type = OP_NONE;
- return segmented_write(ctxt, ctxt->dst.addr.mem,
- &desc_ptr, 2 + ctxt->op_bytes);
+ return segmented_write_std(ctxt, ctxt->dst.addr.mem,
+ &desc_ptr, 2 + ctxt->op_bytes);
}
static int em_sgdt(struct x86_emulate_ctxt *ctxt)
--
2.8.0.rc2.1.gbe9624a
