62 lines
2.1 KiB
Diff
62 lines
2.1 KiB
Diff
From: Steve Rutherford <srutherford@google.com>
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Date: Wed, 11 Jan 2017 18:28:29 -0800
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Subject: KVM: x86: Introduce segmented_write_std
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Origin: https://git.kernel.org/linus/129a72a0d3c8e139a04512325384fe5ac119e74d
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Introduces segemented_write_std.
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Switches from emulated reads/writes to standard read/writes in fxsave,
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fxrstor, sgdt, and sidt. This fixes CVE-2017-2584, a longstanding
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kernel memory leak.
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Since commit 283c95d0e389 ("KVM: x86: emulate FXSAVE and FXRSTOR",
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2016-11-09), which is luckily not yet in any final release, this would
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also be an exploitable kernel memory *write*!
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Reported-by: Dmitry Vyukov <dvyukov@google.com>
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Cc: stable@vger.kernel.org
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Fixes: 96051572c819194c37a8367624b285be10297eca
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Fixes: 283c95d0e3891b64087706b344a4b545d04a6e62
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Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Steve Rutherford <srutherford@google.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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[carnil: backport for 4.9, changes only before 283c95d0e389 in 4.10-rc1]
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---
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arch/x86/kvm/emulate.c | 22 ++++++++++++++++++----
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1 file changed, 18 insertions(+), 4 deletions(-)
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--- a/arch/x86/kvm/emulate.c
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+++ b/arch/x86/kvm/emulate.c
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@@ -791,6 +791,20 @@ static int segmented_read_std(struct x86
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return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception);
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}
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+static int segmented_write_std(struct x86_emulate_ctxt *ctxt,
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+ struct segmented_address addr,
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+ void *data,
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+ unsigned int size)
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+{
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+ int rc;
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+ ulong linear;
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+
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+ rc = linearize(ctxt, addr, size, true, &linear);
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+ if (rc != X86EMUL_CONTINUE)
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+ return rc;
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+ return ctxt->ops->write_std(ctxt, linear, data, size, &ctxt->exception);
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+}
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+
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/*
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* Prefetch the remaining bytes of the instruction without crossing page
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* boundary if they are not in fetch_cache yet.
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@@ -3658,8 +3672,8 @@ static int emulate_store_desc_ptr(struct
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}
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/* Disable writeback. */
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ctxt->dst.type = OP_NONE;
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- return segmented_write(ctxt, ctxt->dst.addr.mem,
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- &desc_ptr, 2 + ctxt->op_bytes);
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+ return segmented_write_std(ctxt, ctxt->dst.addr.mem,
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+ &desc_ptr, 2 + ctxt->op_bytes);
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}
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static int em_sgdt(struct x86_emulate_ctxt *ctxt)
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