On Sat, Feb 06, 2021 at 04:35:48PM +0800, Lecopzer Chen wrote:
> Linux support KAsan for VMALLOC since commit 3c5c3cfb9ef4da9
> ("kasan: support backing vmalloc space with real shadow memory")
>
> Like how the MODULES_VADDR does now, just not to early populate
> the VMALLOC_START between VMALLOC_END.
>
> Before:
>
> MODULE_VADDR: no mapping, no zoreo shadow at init
> VMALLOC_VADDR: backed with zero shadow at init
>
> After:
>
> MODULE_VADDR: no mapping, no zoreo shadow at init
> VMALLOC_VADDR: no mapping, no zoreo shadow at init
s/zoreo/zero/
> Thus the mapping will get allocated on demand by the core function
> of KASAN_VMALLOC.
>
> ----------- vmalloc_shadow_start
> | |
> | |
> | | <= non-mapping
> | |
> | |
> |-----------|
> |///////////|<- kimage shadow with page table mapping.
> |-----------|
> | |
> | | <= non-mapping
> | |
> ------------- vmalloc_shadow_end
> |00000000000|
> |00000000000| <= Zero shadow
> |00000000000|
> ------------- KASAN_SHADOW_END
>
> Signed-off-by: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
> ---
> arch/arm64/mm/kasan_init.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index d8e66c78440e..20d06008785f 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -214,6 +214,7 @@ static void __init kasan_init_shadow(void)
> {
> u64 kimg_shadow_start, kimg_shadow_end;
> u64 mod_shadow_start, mod_shadow_end;
> + u64 vmalloc_shadow_end;
> phys_addr_t pa_start, pa_end;
> u64 i;
>
> @@ -223,6 +224,8 @@ static void __init kasan_init_shadow(void)
> mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
> mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
>
> + vmalloc_shadow_end = (u64)kasan_mem_to_shadow((void *)VMALLOC_END);
> +
> /*
> * We are going to perform proper setup of shadow memory.
> * At first we should unmap early shadow (clear_pgds() call below).
> @@ -241,12 +244,17 @@ static void __init kasan_init_shadow(void)
>
> kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
> (void *)mod_shadow_start);
> - kasan_populate_early_shadow((void *)kimg_shadow_end,
> - (void *)KASAN_SHADOW_END);
>
> - if (kimg_shadow_start > mod_shadow_end)
> - kasan_populate_early_shadow((void *)mod_shadow_end,
> - (void *)kimg_shadow_start);
Not something introduced by this patch but what happens if this
condition is false? It means that kimg_shadow_end < mod_shadow_start and
the above kasan_populate_early_shadow(PAGE_END, mod_shadow_start)
overlaps with the earlier kasan_map_populate(kimg_shadow_start,
kimg_shadow_end).
> + if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
> + kasan_populate_early_shadow((void *)vmalloc_shadow_end,
> + (void *)KASAN_SHADOW_END);
> + else {
> + kasan_populate_early_shadow((void *)kimg_shadow_end,
> + (void *)KASAN_SHADOW_END);
> + if (kimg_shadow_start > mod_shadow_end)
> + kasan_populate_early_shadow((void *)mod_shadow_end,
> + (void *)kimg_shadow_start);
> + }
>
> for_each_mem_range(i, &pa_start, &pa_end) {
> void *start = (void *)__phys_to_virt(pa_start);
> --
> 2.25.1
>
--
Catalin
