| From | Willy Tarreau <> | Subject | [PATCH 3.10 006/250] KVM: x86: Introduce segmented_write_std | Date | Thu, 8 Jun 2017 00:56:32 +0200 |
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From: Steve Rutherford <srutherford@google.com>
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@google.com> Fixes: 96051572c819194c37a8367624b285be10297eca Fixes: 283c95d0e3891b64087706b344a4b545d04a6e62 Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Steve Rutherford <srutherford@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Willy Tarreau <w@1wt.eu> --- 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
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