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| author | Nadav Amit <namit@cs.technion.ac.il> | 2014-10-03 01:10:04 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-10-24 13:21:18 +0200 |
| commit | 08da44aedba0f493e10695fa334348a7a4f72eb3 (patch) | |
| tree | 0a2194efd8b9a542f208337f16a67e8807deb417 /arch/x86 | |
| parent | 2bc19dc3754fc066c43799659f0d848631c44cfe (diff) | |
| download | linux-08da44aedba0f493e10695fa334348a7a4f72eb3.tar.gz linux-08da44aedba0f493e10695fa334348a7a4f72eb3.tar.bz2 linux-08da44aedba0f493e10695fa334348a7a4f72eb3.zip | |
KVM: x86: Decoding guest instructions which cross page boundary may fail
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.
Cc: stable@vger.kernel.org
Fixes: 5cfc7e0f5e5e1adf998df94f8e36edaf5d30d38e
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c0deaff8d9f0..02c8ea804aaf 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -778,8 +778,10 @@ static int __do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt, int op_size) 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; } |