Re: [PATCH v2 4/4] arm64: kaslr: support randomized module area with KASAN_VMALLOC

Will Deacon
2021-01-27T23:22:58Z

On Sat, Jan 09, 2021 at 06:32:52PM +0800, Lecopzer Chen wrote:
> After KASAN_VMALLOC works in arm64, we can randomize module region
> into vmalloc area now.
>
> Test:
> VMALLOC area ffffffc010000000 fffffffdf0000000
>
> before the patch:
> module_alloc_base/end ffffffc008b80000 ffffffc010000000
> after the patch:
> module_alloc_base/end ffffffdcf4bed000 ffffffc010000000
>
> And the function that insmod some modules is fine.
>
> Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
> ---
> arch/arm64/kernel/kaslr.c | 18 ++++++++++--------
> arch/arm64/kernel/module.c | 16 +++++++++-------
> 2 files changed, 19 insertions(+), 15 deletions(-)
>
> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> index 1c74c45b9494..a2858058e724 100644
> --- a/arch/arm64/kernel/kaslr.c
> +++ b/arch/arm64/kernel/kaslr.c
> @@ -161,15 +161,17 @@ u64 __init kaslr_early_init(u64 dt_phys)
> /* use the top 16 bits to randomize the linear region */
> memstart_offset_seed = seed >> 48;
>
> - if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
> - IS_ENABLED(CONFIG_KASAN_SW_TAGS))
> + if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) &&
> + (IS_ENABLED(CONFIG_KASAN_GENERIC) ||

CONFIG_KASAN_VMALLOC depends on CONFIG_KASAN_GENERIC so why is this
necessary?

Will