Re: [PATCH 1/4] target/i386: decode-new: avoid out-of-bounds access to xmm_regs[-1]

[Philippe Mathieu-Daudé]

On 19/10/22 17:06, Paolo Bonzini wrote:
> If the destination is a memory register, op->n is -1.  Going through
> tcg_gen_gvec_dup_imm path is both useless (the value has been stored
> by the gen_* function already) and wrong because of the out-of-bounds
> access.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   target/i386/tcg/emit.c.inc | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/i386/tcg/emit.c.inc b/target/i386/tcg/emit.c.inc
> index 27eca591a9..ebf299451d 100644
> --- a/target/i386/tcg/emit.c.inc
> +++ b/target/i386/tcg/emit.c.inc
> @@ -296,7 +296,7 @@ static void gen_writeback(DisasContext *s, X86DecodedInsn 
> *decode, int opn, TCGv
>       case X86_OP_MMX:
>           break;
>       case X86_OP_SSE:
> -        if ((s->prefix & PREFIX_VEX) && op->ot == MO_128) {
> +        if (!op->has_ea && (s->prefix & PREFIX_VEX) && op->ot == MO_128) {
>               tcg_gen_gvec_dup_imm(MO_64,
>                                    offsetof(CPUX86State, 
> xmm_regs[op->n].ZMM_X(1)),
>                                    16, 16, 0);

Fixes: 20581aadec ("target/i386: validate VEX prefixes via the 
instructions' exception classes")

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>