Re: [PATCH] ppc/spapr: Fix ubsan warning with unaligned pointer access

[Richard Henderson <richard.henderson@linaro.org>]

On 12/16/23 16:14, Daniel Hoffman wrote:
> Found while running QTest with UBsan. Unaligned pointers appear to be
> valid, so moving the read to an explicit memcpy to an intermediate.
> ---
>   hw/ppc/vof.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/vof.c b/hw/ppc/vof.c
> index e3b430a81f4..609a51c645d 100644
> --- a/hw/ppc/vof.c
> +++ b/hw/ppc/vof.c
> @@ -646,7 +646,10 @@ static void vof_dt_memory_available(void *fdt, GArray *claimed, uint64_t base)
>       mem0_reg = fdt_getprop(fdt, offset, "reg", &proplen);
>       g_assert(mem0_reg && proplen == sizeof(uint32_t) * (ac + sc));
>       if (sc == 2) {
> -        mem0_end = be64_to_cpu(*(uint64_t *)(mem0_reg + sizeof(uint32_t) * ac));
> +        /* Pointer may be unaligned */
> +        uint64_t mem0_end_copy;
> +        memcpy(&mem0_end_copy, mem0_reg + sizeof(uint32_t) * ac, sizeof(mem0_end_copy));
> +        mem0_end = be64_to_cpu(mem0_end_copy);

mem0_end = ldq_be_p(mem0_reg + sizeof(uint32_t) * ac);


r~