3.16.84-rc1 review patch. If anyone has any objections, please let me know.
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From: Marios Pomonis pomonis@google.com
commit 3c9053a2cae7ba2ba73766a34cea41baa70f57f7 upstream.
This fixes a Spectre-v1/L1TF vulnerability in x86_decode_insn(). kvm_emulate_instruction() (an ancestor of x86_decode_insn()) is an exported symbol, so KVM should treat it conservatively from a security perspective.
Fixes: 045a282ca415 ("KVM: emulator: implement fninit, fnstsw, fnstcw")
Signed-off-by: Nick Finco nifi@google.com Signed-off-by: Marios Pomonis pomonis@google.com Reviewed-by: Andrew Honig ahonig@google.com Reviewed-by: Jim Mattson jmattson@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com [bwh: Backported to 3.16: Add #include <linux/nospec.h>] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/x86/kvm/emulate.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
--- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -26,6 +26,7 @@ #include <asm/kvm_emulate.h> #include <linux/stringify.h> #include <asm/nospec-branch.h> +#include <linux/nospec.h>
#include "x86.h" #include "tss.h" @@ -4487,10 +4488,15 @@ done_prefixes: } break; case Escape: - if (ctxt->modrm > 0xbf) - opcode = opcode.u.esc->high[ctxt->modrm - 0xc0]; - else + if (ctxt->modrm > 0xbf) { + size_t size = ARRAY_SIZE(opcode.u.esc->high); + u32 index = array_index_nospec( + ctxt->modrm - 0xc0, size); + + opcode = opcode.u.esc->high[index]; + } else { opcode = opcode.u.esc->op[(ctxt->modrm >> 3) & 7]; + } break; default: return EMULATION_FAILED;