This is a note to let you know that I've just added the patch titled
KVM: x86: Decoding guest instructions which cross page boundary may fail
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-decoding-guest-instructions-which-cross-page-boundary-may-fail.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 08da44aedba0f493e10695fa334348a7a4f72eb3 Mon Sep 17 00:00:00 2001
From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
Date: Fri, 3 Oct 2014 01:10:04 +0300
Subject: KVM: x86: Decoding guest instructions which cross page boundary may fail
From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
commit 08da44aedba0f493e10695fa334348a7a4f72eb3 upstream.
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.
Fixes: 5cfc7e0f5e5e1adf998df94f8e36edaf5d30d38e
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -773,8 +773,10 @@ static int __do_insn_fetch_bytes(struct
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;
}
Patches currently in stable-queue which might be from namit@xxxxxxxxxxxxxxxxx are
queue-3.17/kvm-x86-emulator-fixes-for-eip-canonical-checks-on-near-branches.patch
queue-3.17/kvm-x86-check-non-canonical-addresses-upon-wrmsr.patch
queue-3.17/kvm-x86-handle-errors-when-rip-is-set-during-far-jumps.patch
queue-3.17/kvm-x86-emulator-does-not-decode-clflush-well.patch
queue-3.17/kvm-x86-prefetch-and-hint_nop-should-have-srcmem-flag.patch
queue-3.17/kvm-x86-fix-wrong-masking-on-relative-jump-call.patch
queue-3.17/kvm-x86-decoding-guest-instructions-which-cross-page-boundary-may-fail.patch
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