Re: [PATCH v3 3/5] treewide: use get_random_u32() when possible

Christophe Leroy
2022-10-06T17:21:36Z

Le 06/10/2022 à 18:53, Jason A. Donenfeld a écrit :
> The prandom_u32() function has been a deprecated inline wrapper around
> get_random_u32() for several releases now, and compiles down to the
> exact same code. Replace the deprecated wrapper with a direct call to
> the real function. The same also applies to get_random_int(), which is
> just a wrapper around get_random_u32().
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Acked-by: Toke Høiland-Jørgensen <toke@toke.dk> # for sch_cake
> Acked-by: Chuck Lever <chuck.lever@oracle.com> # for nfsd
> Reviewed-by: Jan Kara <jack@suse.cz> # for ext4
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---

> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 0fbda89cd1bb..9c4c15afbbe8 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -2308,6 +2308,6 @@ void notrace __ppc64_runlatch_off(void)
> unsigned long arch_align_stack(unsigned long sp)
> {
> if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
> - sp -= get_random_int() & ~PAGE_MASK;
> + sp -= get_random_u32() & ~PAGE_MASK;
> return sp & ~0xf;

Isn't that a candidate for prandom_u32_max() ?

Note that sp is deemed to be 16 bytes aligned at all time.

Christophe