On Mon, Dec 13, 2021 at 10:54 PM <andrey.konovalov@xxxxxxxxx> wrote:
>
> From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> Make KASAN unpoison vmalloc mappings after that have been mapped in
> when it's possible: for vmalloc() (indentified via VM_ALLOC) and
> vm_map_ram().
The subject says "don't unpoison VM_ALLOC pages", whereas the
description says "unpoison VM_ALLOC pages", or am I missing something?
> The reasons for this are:
>
> - For vmalloc() and vm_map_ram(): pages don't get unpoisoned in case
> mapping them fails.
> - For vmalloc(): HW_TAGS KASAN needs pages to be mapped to set tags via
> kasan_unpoison_vmalloc().
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> ---
>
> Changes v2->v3:
> - Update patch description.
> ---
> mm/vmalloc.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 58bd2f7f86d7..9a6862e274df 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2208,14 +2208,15 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
> mem = (void *)addr;
> }
>
> - mem = kasan_unpoison_vmalloc(mem, size);
> -
> if (vmap_pages_range(addr, addr + size, PAGE_KERNEL,
> pages, PAGE_SHIFT) < 0) {
> vm_unmap_ram(mem, count);
> return NULL;
> }
>
> + /* Mark the pages as accessible after they were mapped in. */
> + mem = kasan_unpoison_vmalloc(mem, size);
> +
> return mem;
> }
> EXPORT_SYMBOL(vm_map_ram);
> @@ -2443,7 +2444,14 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
>
> setup_vmalloc_vm(area, va, flags, caller);
>
> - area->addr = kasan_unpoison_vmalloc(area->addr, requested_size);
> + /*
> + * For VM_ALLOC mappings, __vmalloc_node_range() mark the pages as
> + * accessible after they are mapped in.
> + * Otherwise, as the pages can be mapped outside of vmalloc code,
> + * mark them now as a best-effort approach.
> + */
> + if (!(flags & VM_ALLOC))
> + area->addr = kasan_unpoison_vmalloc(area->addr, requested_size);
>
> return area;
> }
> @@ -3104,6 +3112,12 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
> if (!addr)
> goto fail;
>
> + /*
> + * Mark the pages for VM_ALLOC mappings as accessible after they were
> + * mapped in.
> + */
> + addr = kasan_unpoison_vmalloc(addr, real_size);
> +
> /*
> * In this function, newly allocated vm_struct has VM_UNINITIALIZED
> * flag. It means that vm_struct is not fully initialized.
> @@ -3799,7 +3813,11 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
> }
> spin_unlock(&vmap_area_lock);
>
> - /* mark allocated areas as accessible */
> + /*
> + * Mark allocated areas as accessible.
> + * As the pages are mapped outside of vmalloc code,
> + * mark them now as a best-effort approach.
> + */
> for (area = 0; area < nr_vms; area++)
> vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
> vms[area]->size);
> --
> 2.25.1
>
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--
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