On Sun, Jan 27, 2019 at 09:29:42AM +0100, Ard Biesheuvel wrote:
> Commit 1598ecda7b23 ("arm64: kaslr: ensure randomized quantities are
> clean to the PoC") added cache maintenance to ensure that global
> variables set by the kaslr init routine are not wiped clean due to
> cache invalidation occurring during the second round of page table
> creation.
>
> However, if kaslr_early_init() exits early with no randomization
> being applied (either due to the lack of a seed, or because the user
> has disabled kaslr explicitly), no cache maintenance is performed,
> leading to the same issue we attempted to fix earlier, as far as the
> module_alloc_base variable is concerned.
>
> Note that module_alloc_base cannot be initialized statically, because
> that would cause it to be subject to a R_AARCH64_RELATIVE relocation,
> causing it to be overwritten by the second round of KASLR relocation
> processing.
>
> Fixes: f80fb3a3d508 ("arm64: add support for kernel ASLR")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.6+
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> arch/arm64/kernel/kaslr.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> index ba6b41790fcd..b09b6f75f759 100644
> --- a/arch/arm64/kernel/kaslr.c
> +++ b/arch/arm64/kernel/kaslr.c
> @@ -88,6 +88,7 @@ u64 __init kaslr_early_init(u64 dt_phys)
> * we end up running with module randomization disabled.
> */
> module_alloc_base = (u64)_etext - MODULES_VSIZE;
> + __flush_dcache_area(&module_alloc_base, sizeof(module_alloc_base));
Do we need something similar of memstart_offset_seed? If yes, you could
as well change the returns to a goto out.
--
Catalin
