On Wed, Mar 25, 2020 at 5:13 PM <glider@xxxxxxxxxx> wrote:
>
> KMSAN assumes shadow and origin pages for every allocated page are
> accessible. For pages in vmalloc region those metadata pages reside in
> [VMALLOC_END, VMALLOC_META_END), therefore we must sync a bigger memory
> region.
>
> Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
> To: Alexander Potapenko <glider@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: Marco Elver <elver@xxxxxxxxxx>
> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> ---
>
> Change-Id: I0d54855489870ef1180b37fe2120b601da464bf7
> ---
> arch/x86/mm/fault.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index a51df516b87bf..d22e373fa2124 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -331,11 +331,21 @@ static void dump_pagetable(unsigned long address)
>
> void vmalloc_sync_mappings(void)
> {
> +#ifndef CONFIG_KMSAN
> /*
> * 64-bit mappings might allocate new p4d/pud pages
> * that need to be propagated to all tasks' PGDs.
> */
> sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
> +#else
> + /*
> + * For KMSAN, make sure metadata pages for vmalloc area and modules are
> + * also synced.
> + */
> + sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_META_END);
> + sync_global_pgds(MODULES_SHADOW_START & PGDIR_MASK,
> + MODULES_ORIGIN_END);
> +#endif
> }
>
> void vmalloc_sync_unmappings(void)
> @@ -360,7 +370,17 @@ static noinline int vmalloc_fault(unsigned long address)
> pte_t *pte;
>
> /* Make sure we are in vmalloc area: */
> +#ifdef CONFIG_KMSAN
> + /*
> + * For KMSAN, make sure metadata pages for vmalloc area and modules are
> + * also synced.
> + */
> + if (!(address >= VMALLOC_START && address < VMALLOC_META_END) &&
> + !(address >= MODULES_SHADOW_START &&
> + address < MODULES_ORIGIN_END))
> +#else
> if (!(address >= VMALLOC_START && address < VMALLOC_END))
> +#endif
> return -1;
>
> /*
> --
> 2.25.1.696.g5e7596f4ac-goog
>
