3.16.41-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Steve Rutherford <srutherford@xxxxxxxxxx>
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 <dvyukov@xxxxxxxxxx>
Fixes: 96051572c819194c37a8367624b285be10297eca
Fixes: 283c95d0e3891b64087706b344a4b545d04a6e62
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Steve Rutherford <srutherford@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
[bwh: Backported to 3.16: drop changes to em_fxsave(), em_fxrstor()]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -744,6 +744,20 @@ static int segmented_read_std(struct x86
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.
@@ -3268,8 +3282,8 @@ static int emulate_store_desc_ptr(struct
}
/* 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)