| Message ID | CAKv+Gu9RbzCNi-UHbL52rP=vtfutxqy8Vkn=WkQ-UQqo2Csdmg@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On Fri, Jan 08, 2016 at 11:59:44AM +0100, Ard Biesheuvel wrote: > This works, as far as I can tell. However, I still need the patch > below to make sure that the KAsan zero page is mapped read-only. (The > reason is that, depending on the alignment of the regions, > kasan_populate_zero_shadow() may never call > zero_[pud|pmd|pte]_populate()) > > Before this patch (and my change), the KAsan shadow regions looks like this: > > 0xffffff8000000000-0xffffff8200800000 8200M RW NX SHD AF UXN MEM/NORMAL > 0xffffff8200800000-0xffffff8200c00000 4M RW NX SHD AF BLK UXN MEM/NORMAL > 0xffffff8200c00000-0xffffff8800000000 24564M RW NX SHD AF UXN MEM/NORMAL > 0xffffff8800000000-0xffffff8820200000 514M RW NX SHD AF BLK UXN MEM/NORMAL > > and after: > > 0xffffff8000000000-0xffffff8200800000 8200M ro NX SHD AF UXN MEM/NORMAL > 0xffffff8200800000-0xffffff8200c00000 4M RW NX SHD AF BLK UXN MEM/NORMAL > 0xffffff8200c00000-0xffffff8800000000 24564M ro NX SHD AF UXN MEM/NORMAL > 0xffffff8800000000-0xffffff8820200000 514M RW NX SHD AF BLK UXN MEM/NORMAL > > > ---------8<-------------- > diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c > index 72fe2978b38a..c3c14204d196 100644 > --- a/arch/arm64/mm/kasan_init.c > +++ b/arch/arm64/mm/kasan_init.c > @@ -140,6 +140,7 @@ void __init kasan_init(void) > { > u64 kimg_shadow_start, kimg_shadow_end; > struct memblock_region *reg; > + int i; > > kimg_shadow_start = round_down((u64)kasan_mem_to_shadow(_text), > SWAPPER_BLOCK_SIZE); > @@ -185,6 +186,14 @@ void __init kasan_init(void) > pfn_to_nid(virt_to_pfn(start))); > } > > + /* > + * KAsan may reuse the current contents of kasan_zero_pte > directly, so we > + * should make sure that it maps the zero page read-only. > + */ > + for (i = 0; i < PTRS_PER_PTE; i++) > + set_pte(&kasan_zero_pte[i], > + pfn_pte(virt_to_pfn(kasan_zero_page), PAGE_KERNEL_RO)); > + > memset(kasan_zero_page, 0, PAGE_SIZE); > cpu_replace_ttbr1(swapper_pg_dir); That's complementary to my patch. Could you please send it with a proper description so that Will can pick them up? For your patch: Acked-by: Catalin Marinas <catalin.marinas@arm.com> -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c index 72fe2978b38a..c3c14204d196 100644 --- a/arch/arm64/mm/kasan_init.c +++ b/arch/arm64/mm/kasan_init.c @@ -140,6 +140,7 @@ void __init kasan_init(void) { u64 kimg_shadow_start, kimg_shadow_end; struct memblock_region *reg; + int i; kimg_shadow_start = round_down((u64)kasan_mem_to_shadow(_text), SWAPPER_BLOCK_SIZE); @@ -185,6 +186,14 @@ void __init kasan_init(void) pfn_to_nid(virt_to_pfn(start))); } + /* + * KAsan may reuse the current contents of kasan_zero_pte directly, so we + * should make sure that it maps the zero page read-only. + */ + for (i = 0; i < PTRS_PER_PTE; i++) + set_pte(&kasan_zero_pte[i], + pfn_pte(virt_to_pfn(kasan_zero_page), PAGE_KERNEL_RO)); + memset(kasan_zero_page, 0, PAGE_SIZE); cpu_replace_ttbr1(swapper_pg_dir);